[throwanem]

"Why can't I do light editing and post to Instagram directly from the camera?"

Because the computing resource, battery power, and physical volume spent on hardware Instagram integration detracts from what can be devoted to making the camera as good as possible at being a camera. You'd have to cram a smartphone in there, and everyone already has smartphones anyway.

And you can do light editing in-camera, if you want.

"Why can't download the photos directly to a phone? Why can't I charge from a micro-USB/USB-C cable?"

You can. Modern bodies have touchscreens, too.

And I don't want Nikon and Canon worrying about marketing to influencers, because influencers are a terrible market! I want them worrying about making and selling excellent cameras for the use of people who do need more than a phone camera or maybe a cheap camcorder can provide.

[zazaraka]

By catering to influencers in SOME models, they would be in a much better financial shape to continue R&D for the pros.

[throwanem]

They already do, with their prosumer lines. Mommy bloggers, for example, have a surprising amount to say about how to get the most out of a Nikon D3300 or similar; I actually got some useful tips from them back when I was just starting out with my first D5300.

Granted, the camera makers haven't gone to the extent of just building a smartphone into a DSLR so you can post to Instagram with two taps, or whatever. IMO that's because they know where their strengths lie, and also understand that such a hybrid device would need a few generations to evolve into really solid usability - generations which it would not receive, because the same market at which it'd be aimed would consider the v1.0 difficulties a deal breaker for exactly the ease-of-use reasons you're arguing it would be a good idea for the camera makers to do this in the first place.