I am not sure who can define what a plug-in is or is not supposed to do…
MIDI CC messages are just MIDI messages like others, so you may want to convert them to other types of messages (for example CC to program change for controllers that cannot do Program Change), pass them to other plug-ins hosted inside a plug-in etc.
As you may already know, we have the same problem with Program Change messages. The “program” function provided by VST3 being buggy and incompatible with what program change usually does (mainly in Steinberg hosts btw) makes it completely useless, so people expect to have simple MIDI support.
Musicians are used to dealing with MIDI in general, so there is no reason for removing it (do you plan to remove raw audio data support as well in the future?). How do you explain customers that they can create MIDI tracks to store MIDI events but cannot process / receive them properly in plug-ins?