Because if they put latches in, they have to be certified by NHTSA - and that takes 9 months. And the Feds wouldn't give them a waiver or allow any time for certification, so out the switches went (I do some work for a company here in Dallas tha makes parts for the switches). Should also be noted that the Tundra is being replaced this year anyway, and it DOES have the certified latches in it.
Of course, they could still have done things the right way - or easier yet, do them the right way the first time. This isn't rocket science where you have some unknown combination of factors that result in a problem - it was clearly spelled out in the law.