Far more successful devs disagree.
I think you're confusing "developper" as a company and "developper" as a work.
One thing I can guarantee you - the skillset to develop games has absolutely nothing in common with the one to manage community. Some guys have both, but you don't recruit your C++ coder because he can do PR speech on a forum - it's just a happy coincidence, or you're recruiting for a post with multiple aspects.
Notice : I don't mean that dev CAN'T or SHOULDN'T post on forums. I mean it's not their work, and you can't expect that from them. And if they do, holding them to super-high standard and being vindicative toward them is going to burn them out of posting after a while.
Paradox, Blizzard, Frontier Developments and CDPR would like to disagree with you there.
No they won't. It's not because they DO interact that it's their JOB.
Blizzard dev actually rarely post outside of the one or two official spokepersons, the rest are actual community manager.
Paradox and CDPR do it because there is less antagonism/toxicity there, but if they start to be subject to regular abuse and insult, you can bet they'll stop. You can also bet they do it mainly outside their working hours - because, again, it's not their job. They do it because they love it, because interacting with fans, when it's constructive, is extremely gratifying and rewarding. If fans start to act like entitled dicks and turn their pleasure into annoyance, they'll stop. That's as simple as that, and that's pretty much in line with what happened to Bioware dev.