For the recent generations, with some limited exceptions, it pretty much is.

The early named ones were based around major social/economic issues that influenced them as they grew up - WWI, Great Depression, WWII - and then Baby Boomers created a sort of wave pattern in the population that made for easy groupings into the future.

That wave pattern has since become much flatter, if not disappeared completely, but the idea is pretty appealing so it persists. You will occasionally see it start to break down though, for example with "Millennial" being split into young and old.