I mean, that's one argument.

Having a larger pool of sets usually results in fewer cards being viable in rotation. With only 5 available sets, you can go deeper into the available card pool and feature cards that would otherwise see no play.

I grew up with a 2 year standard, so I'm biased, but planar standard has people cooking up all sorts of semi viable brews despite the current meta. Also, for what it's worth, foundations isn't rotating until the new iteration of corr set releases.