From my experience I have noted that those hobbyists who could read music played music much later in life than those who could not read music. That is when ones music genre went out of style they put down their instruments.

I'd surmise that those pros who could not read music were surrounded but those that could read music, either with session musicians or for transcription of what they played for copyright publishing purposes. YMMV

But,as already noted, you do not need to read music to produce good music.

Whenever I get something stuck in the back of my throat, I dislodge it by drinking a beer.
It's called the Heineken Maneuver.

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware