Another thought is this.
Since Tiger Woods came on the scene, the amounts of money these guys are making is obscene.
Prior to that, say in the 90's, regular tour events meant more because players were not really financially set like they are today. For instance, any player who is out there (PGA Tour) today is making multi-million dollars per year when you add up winnings and endorsements.
So the Walmart Classic is meaningless to a guy like Rickie Fowler because in a way, the only way to really improve his legacy is to win a major or two. He's got enough money. Yea, he could rack up another win, but I think most guys like him are using non-major events as tune ups for the majors and to stay competitive.
The other thing to keep in mind is if a player does win a major, his endorsement deals skyrocket. See Danny Willett.
So to summarize, majors put players in the history books and mean more money.
Yea, majors aren't everything but they are 90% of the pie and getting to be a larger piece each season.