Deleted Personally I haven't seen musical instruments "trickle down" to lower classes. The latter are still mainly concerned with screen entertainment (TV, streaming and video games).
I think it was Larry Fine who attributed the decline to the media, starting over a century ago. First the phonograph. Then radio. Those are cheap. And require no skill. So the piano went into decline.
When he wrote that it was well before the explosion of internet based media. The decline continues.
As for other instruments holding their own ... keep in mind that other instruments are far cheaper than an acoustic piano. Even a cheap, low-end console costs over $3000. You can get started on a guitar for far less money.
Also, high-school bands (and middle school, too) are the starting point for many young musicians. It's hard to march in a band with a piano keyboard, eh? So the latter is absent from that curriculum. My girls played flute, piccolo, and clarinet.
My eldest picked up a little (self-taught) piano just because I had an upright in the house. But she's now grown, married, and has a son ... and no piano. But she finds plenty of time for "the media" ... like binge watching whatever show is new, hip, and cool on Netflix.