That's just incorrect due to the sheer exponential increase of humans alive, not to mention the many cultural factors you are ignoring. Thousands of bands were started because kids heard old blues music over the radio and became inspired.
I'd wager there's more bands and venues than ever now and if anything, I'm seeing more and more people make a living off their music thanks to the network effects of social media combined with touring. I've watched two of my friend's bands - pretty weirdo stoner pop music - go on national tours supporting major acts (Of Montreal was one) and it most likely would've never happened if not for the exposure and channels of the internet.