Variant E6/P6: why are adults 1st level?

[Fizban]

2) first-level PCs should be competent:

First level PCs are already competent. They are only "incompetent" when one deliberately sets their baseline above the one the game actually uses, which is 1st level non-elite NPC classes for 95% of people.

(Yes, I did use the phrase "pitifully weak," which is in relation to the every increasingly powerful monsters you're expected to take on with not even half a dozen people, not the rest of the population.)