Why does OCSP stapling even exist?

Because querying the OCSP servers directly results in a crazy amount of traffic.

Implemented in the most paranoid manner possible every https request would result in an OCSP request.

That would be millions of requests per second for a large CA.

They have effectively no financial interest in actually supporting that.

More importantly, it removes the privacy leak from client to CA, since the client is no longer speaking to the CA directly (it just has to look at the signature).