If payment protocol was not supported people would be complaining about lack of support for the new merchant integration methods.
Who did complain?
If payment protocol is distributed with Core, it should be an optional thing, which the user can decide to activate (by checkbox, whatever). Security is much more important.
Edit. imho the dialog introduced in 0.9.0 which replaced the receiving addresses field is not an improvement. It makes things more awkward. (An example of a really good improvement is coincontrol and wallet file selection.)