Because somebody needs to keep things running for the rest of us?

Seriously, we need all the bright people we can get, working on the tough problems and solving them. And we need even more basically competent people educated to keep what we have got figured out running smoothly. Life isn't some role playing game where everyone who wants to should get a turn being a surgeon or flying the jumbo jet. Competence actually matters.

The people that designed jumbo jets were people that went to Washington State University and UDub in the 60s. John Aaron saved Apollo 12 and 13 with a degree from Southwestern Oklahoma State. These are not people that were in “gifted programs” and they don’t fit what you perceive to be “gifted” (aka - able to get into one of 10 elite undergrad schools).