You don't expect common sense from FIFA, but this takes the biscuit.
If they were really concerned about possible ill-effects on players' health, they'd ban internationals in all manner of extreme conditions, but they've happily played several World Cups in sauna-like temperatures, and at the hottest times of day, to maximise their TV income. Oh, and usually while preventing players from taking on water during the game (remember USA '94?). Interesting that the maximum altitude is set just high enough to allow Mexico City to carry on as a venue - too big a market to alienate, I presume.
No, this is about stopping the countries concerned gaining a so-called 'unfair advantage', although no one explains how it's not also unfair when the players of, say, Ecuador, have to travel to some steamy, low altitude smog-basin to play. It's about making life easy for the big boys of world football, because they've suffered the odd embarrassment at altitude in the past.
Let's face it, what FIFA really want is the same relatively few nations battling it out all the time. Don't dress it up as concern over players' health.
There, conspiracy theory rant over!