I wouldn't say that it was because other world powers depended on them, but it certainly did become a haven for many powerful and influential people (and their wealth). Their ability to stay neutral had everything to do with location.

Firstly, it's smack dab in the middle of France, Italy, Germany, and Austria, allowing trade with at least two parties in the wars at all times. Even at the height of Axis conquest, when Switzerland was completely surrounded by Germany and Italy, it still had bargaining power via its control of the trans-alpine rail tunnel that connected the two.

Second, it's in the mountains. This automatically made them a difficult target to attack, one that would require diverting significant resources from other, more important fronts that were already being contested. And of course, in the case of the Axis, trade would be severely hampered until that conflict was resolved.

Third, the Swiss were very prepared to deal with attacks from any side. They mobilized the entire country very quickly in both wars, and their strategy was all about attrition and deterrence. Strongly defensive positions had been setup in the alps across the country, loaded with enough provisions to hold out for a good while.

That all said, it wasn't that Germany couldn't conquer them, but rather it just wouldn't be worth the trouble when they were already engaged on so many other fronts.

Speaking only to World War II, I've written about the Swiss position previously, so this old answer may be of interest to you. Happy to answer follow ups best that I can.