a.) you would say that, wouldn't you, you'd like as much of PG's attention as possible
b.) it's quite presumptious to state that the 1000s of others would be lower quality. Are the less than 1000, mid 20s, mostly male, mostly american, applicants to YC the best candidates on earth?
There are probably 1000x, if not more, capable founders of all age groups, nationalities, and genders that PG could get a slice of. He's built a brand and should seek to capitalize on it before someone establishes a superior brand.
Off course, this all about what PG does for fun, he's already rich enought to never work again. It might be that he enjoys mentoring a few founders a couple of times a year and doesn't have global ambitions.