The 55+ demo is approximately the top half or so of baby boomers...and that's a LOT of humans.
Myself...I don't own a smartphone. I think it'd be cool...but, I can't get past having to pay an extra $30-50/month just to listen to different radio stations...and having to run patch cords into my car radio, put on headphones, or patch into a computer.
I have a few thousand songs on my MP3 player...I continue to add to it, and while that's not like radio/streaming stations....it's far cheaper, and a lot, lot more convenient.
Android smartphones and plans are getting cheaper by the day. Currently, I pay $40 a month for a plan that includes 1200 minutes and unlimited texting (all smartphone plans have unlimited text) and data usage (which is highly recommended for people that listen to streaming services). You don't have to pay through the nose for an iPhone plan.
I listen to a lot of streaming radio in the car and at home, and quite enjoy it.
The cables can be somewhat of a hassle but I have a cassette deck in my car, and use an adapter for it. Works the same way as plugging in an mp3 player.
In addition, the apps are becoming easier to use. Pandora is pretty simple, as is IHeartRadio. TuneIn can be a bit more complicated for technophobes, but its still a great app.