Because it’s not fully working well yet. For example people have reported issues when using server actions in a statically rendered route

what kind of issues (getting no reponse, internal server error, no error handling, ...)? Is the risk huge to make me rewrite my server actions in route handlers?

you can see it in nextjs github repo. With the question of risk . USE it at your own risk . It is not recommended because there might be a big changes that might happen and would make you re write most of your codebase.

I would say the risk is not huge, but it is there