What makes you think the Revolutionary War wasn't a civil war, or that the Civil War wasn't a revolutionary one? The naming convention is just for convenience and legacy, and perhaps because the ultimately consequences of a civil conflict are quite different depending on who comes out on top.

The Revolutionary war was certainly seen as a civil war, a war within the state. Thousands of colonial Loyalists fought for the Crown, and politicians on both sides of the Atlantic saw themselves as fundamentally English. The conflict was ultimately over whether colonials, especially the colonial elite, had the same rights and privileges that subjects in the home country and where authority ultimately lay. That's a fundamentally civil dispute.

The Civil War, likewise, was seen by many of its combatants as revolutionary. It was a revolt by the slave-holding elite of the South, playing up a distinctive Southern nationalism that rallied their populace, to upend the new political order signaled by the victory of the Republicans in the North. Southern leaders created a new Constitution that aped the original to a great degree, but specifically enshrined slavery in a way that the compromises of the old order hadn't allowed. It was revolutionary in that sense.