Track bikes and road bike manufacturers

So in my quest for a good second hand track bike, I have some older frames from big name manufacturers (Cannondale, Specialised, Basso, etc etc). However, it sems like basically all of these frames were discontinued quite a few years ago, and now it seems that the only really affordable frames that are made these days are Dolans and Condors.

My question is, why have all these big companies stopped making track frames? I can't imagine it's got anything to do with research, as they put so much money into their R&D that some of it has to transfer across from the road to the track.
-What would be wrong with just swapping out the rear dropouts for track dropouts, getting rid of any brake/gear hardware and maybe lifting the BB? That seems so simple
-For example, why don't Cannondale just tweak their systemsix and put out an aero, stiff track bike?

What am I missing here?

Niche market, low margins

Nobody would buy it

Caad10 track did just that, retailer's found them difficult to shift in large enough numbers to make the whole project viable, it's wasn't repeated.

Used to be a big crossover with track frames to the fixie/commuter market as well. That's not really there anymore, so could be why they've all stopped?

On a related noted, have Planet X thrown in the towel as well? Can't see any track bikes, frames or wheels on their site...

I was thinking that as well