You can only buy real estate with bitcoin IF the government in which where you are trying to buy real estate allows it, so at least when it comes to real estate, bitcoin is still subjected to government approval, therefore the state/government has an huge amount of control on what bitcoin can do. Not being able to buy real estate with it is a constant sell pressure for bitcoin since anyone wanting to do real estate business is forced to take a pretty big dump for fiat first. This is a problem.

If one could buy real estate directly with bitcoin, you would give the real estate to the owner and this bitcoin would (in principle) be converted back to fiat. Now the owner can do whatever he wants but at least it isn't a requirement.

I know some people has bought real estate with BTC but these cases are still:

1) Marginal
2) Still has government approval otherwise it wouldn't be happening