Because it would be incredibly unpopular, for one.
Can you imagine being in the middle of some work, Googling a term, only to be hit with "Sorry, we're over the government limit and can't fulfill your search"
Hacker News and Stack Overflow would be full of people trading tips about using VPNs to evade the limits.
People don't actually like having the government restrict them from using things they want to use.
Please ask about VPNs on Quora until the end of the month.
You're right, I hate it and always switch to a different search engine instead. So, that's the goal here right?
You using a VPN is just as outrageous to them as you attempting to use a working ad blocker.
Programmers are often overconfident and think they can implement anything... except when they have to follow common sense regulation in which case it's always impossible or they come up with ridiculous straw men like you just have.
There are a million ways to curtail anti-competitive behavior. One, on the spot, example would be: not to stop people from making searches, but instead to tax at 100% everything over the 30% of searches.