I have four kids. All but one of them, with some firm but not mandatory prodding from us, took up a band instrument in school, generally at 5th grade in our systems around here. Eldest daughter (now 22) did clarinet, 2nd opted out, son did saxophone, youngest (now 10) trombone.
The older two also took piano lessons from my cousin; the 2nd later switched to guitar, but really was always reluctant about instruments (she's terribly introverted and doesn't like doing things people can hear her at). The oldest didn't keep up piano lessons forever, but the last couple of times she came home I noticed that the first thing she did after setting down her suitcases was to go to the living room piano and play.
My son (only boy, 3rd child) tinkered with guitar and took drum lessons for a while, but never really followed through with either. Sax is his instrument. He hasn't done too much with it lately but hasn't entirely lost touch with it either.
My youngest (the 10-year old) when she was about 7 heard my sister playing violin and was fascinated by it, so we bought her one for her 8th birthday and she had lessons for a year or two. Unfortunately we had to stop them for financial reasons, but she has expressed interest in resuming, and we should be in a position to do that soon. As I said, she has taken up trombone in school. I bought her a little Daisy Rock guitar and we had one session learning to play it, but it hasn't really captured her attention. She will also spontaneously sit at one of the keyboards in the house and figure stuff out on them, though she's never had a lesson.
Overall, I think my kids' experience with music is not too different from my own thirty and forty years ago. I had a bit of piano lessons, didn't stick with it, took up sax as a band instrument for five years, then let that go to focus on drama club. Tinkered a bit with drums and bass but never seriously. I picked up mandolin when I was a camp counselor my college years and that was the only instrument I banged around on for years, until at the age of 38 I was bitten by the bass bug and got serious about it. Bass also led to guitar a couple of years later that I tinker on casually and play in church.
While I can hear the generational implications in the question and none of my kids were sort of Beatles-on-Ed-Sullivan inspired, guitar-obsessed kids who ate, drank, and slept guitar... neither was I, in the 80s, nor most kids I knew. My son does have a good friend from high school who IS guitar-obsessed and now plays in a death metal band, though, so I don't think the phenomenon has disappeared.