Alright, I just heard an actually decent reason to the lack of technology in FIFA approved football...
If they made it a rule, it would leave out lots of poorer countries that could just not afford the infrastructure needed to implement the technological checkings. Think of countries where football is the national pastime but are still poor as hell, someone like Trinidad & Tobago, they would have to leave FIFA if they wanted to continue playing football in their local league. Which would mean no international tournament inclusion, no FIFA-approved league, no way of their players playing in other countries... it'd be pretty bad.
I'm not saying it's the only reason they would need, they could just require the technology during international tournaments, but it's the first time I've heard an actual reason for their lack of technology that makes some sense.