Maybe it was disabled mainly because of this:
Unfortunately, the implementation provided no authentication, so any "man in the middle" could have intercepted your bitcoins during the transaction. When they see that you're sending a Bitcoin payment by IP address, they pretend to be the actual destination and send back their Bitcoin address. You end up sending bitcoins to the wrong person. It's therefore no longer a good idea to send bitcoins in this way, especially if you're using a proxy.
https://en.bitcoin.it/wiki/IP_transactionThere was some discussion in this old thread:
[pull] Remove send to IP address and IP transactions supportI'm certain is due to this, any hard coded security risk needs to go, and this could become a very big problem early on, maybe there are better technologies now, but I think it's better we didn't risk it until new technologies were available.