I have an old o"neil supersuit drysuit, with oral inflator. I use it for free diving in the Puget Sound, and since there is no other way to add air, except by mouth, I would prefer to have the option to add an oral inflator to a new drysuit. Few people free dive and snorkel in Cold water,
I so some solo diving, and the oral inflator can provide a backup to a failed inflator hose, even as a back-up BC. Although I doubt that is likely to happen, a lot of people swear by making everything redundant, just in case Murphy applies his law to your dive.
If it ain't broke...