There are three reasons why there have only been 17 amendments in 200+ years of constitutional government. It doesn't have anything to do with "reverence". First, the legal barriers to changing the Constitution are enormous. Second, the federal judiciary is empowered to reinterpret a 200-year-old document according to contemporary morals and standards. Third, the relatively limited nature of the federal government compared to unitary states like France or England means that much (if not most) day-to-day governance is carried out at the state level, and state constitutions change all the time.

1. Legal barriers. Amendments are rare, and nearly impossible to pass. It requires a supermajority in both houses of Congress to submit an amendment to the states for ratification, and 3/4 of states must approve an amendment to enshrine it in the Constitution. This kind of political unity is damn-near impossible to achieve and happens maybe twice a century. As such, it's not an accident that amendments generally happen in clusters. (Notably, during the Civil War, when the Confederates wrote their new constitution, they reduced the 3/4 threshold for ratification of an amendment to 2/3, believing-- correctly-- that it was too hard to pass an amendment with a 3/4 threshold.)

   Tellingly, there are only a few times this relative unity has existed. First is the Bill of Rights (1-10), passed as part of the compromises between Federalists and Anti-Federalists to get the Constitution through in 1789. Fast-forward 75 years, and you have the Reconstruction Amendments (13-15), intended to secure the rights of blacks and defang the Confederacy after the Civil War. Following those are the Progressive-era amendments of 1910-20, (16-19), which were intended to fix the excesses of the Gilded Age by banning alcohol, giving women the vote, direct popular election of senators, and legalizing the income tax. Most recently, we have the cluster of amendments in the 1960s and early 1970s that coincide with the great social movements of the era-- lowering the voting age to 18 and banning the poll tax, as well as giving the District of Columbia voting rights in presidential elections.

2. The federal judiciary. The difficulty of amending the text of the Constitution, combined with the American common law tradition, has led to a federal judiciary with an unusual degree of latitude in interpreting the country's basic document and adapting it to modern times. Let's use the due process clause of the 14th Amendment as an example.

   This clause reads, "No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws." At various times, the judiciary has held that that clause prevents the states from regulating business. Lochner v. New York, 198 U.S. 45 (1905). Other times, it has held the exact opposite, as the political winds drifted the other way. West Coast Hotel Co. v. Parrish, 300 U.S. 379 (1937).

   Later, in the 1960s, the doctrine used in Lochner to justify a ban on workplace regulation was used to legalize interracial marriage, Loving v. Virginia, 388 U.S. 1 (1967), and establish the right to privacy. Griswold v. Connecticut, 381 U.S. 479 (1965). This doctrinal flexibility is decidedly characteristic of American jurisprudence-- partly because the Constitution is just so damn hard to amend.

3. State governments. The U.S. is big. Really, really big. It's the third-largest country on the planet both by population and by area, and most day-to-day governance is not dictated from Washington D.C. The states are held to a certain baseline by the federal constitution and federal laws, but most local government is just that-- local government. Infrastructure, labor regulation, economic development, consumer protection, law enforcement, and public education are all handled largely at the state level, and that's just the tip of the iceberg. (Don't believe me? Let's put it this way: the FBI has 35,000 employees-- and the New York City Police Department alone has 50,000.)

   Now, don't get me wrong. The federal government certainly helps the states out with funding for government programs, but the state governments are the ones who shoulder most of the load of day-to-day governance. Thus has it always been. So, when the South seceded in 1860, there was continuity of government. The seceding states were able to more or less seamlessly assume responsibility for formerly-federal functions.

   By and large, state constitutions are much more flexible in structure than their federal counterpart, and they vary widely in quality, length, and detail. Partly it's because states are smaller than the federal government, and partly it's because their constitutions are generally fairly easy to amend-- California, in particular, is infamous for constantly tinkering with its state constitution by referendum. Tiny Vermont, on the other hand, is still using its constitution from 1793.

   Because state governments are generally adaptable and varied in a way the federal constitution isn't, the federal constitution is a baseline for the rest of the country, but there's nothing stopping states from granting more extensive rights. For example, Florida explicitly limits defendants' rights to the federal baseline for illegal search and seizure. Fla. Const., Art. I, § 12. But California, in contrast, has more stringent standards for illegal search and seizure than the federal baseline. See In re Lance W., 37 Cal.3d 873 (1985). Both of these practices aren't just kosher-- they're actually encouraged by the way the government is structured.

tl;dr: Changing the federal constitution is really really hard, and the states are the ones doing most of the governing anyway

sources: Friedman, The Will of the People; Okrent, Last Call; Sullivan and Feldman, Constitutional Law; McPherson, Battle Cry of Freedom

edit: batsignal u/amescg