I've never developed the habit of doing much resistance training. But I've always known that stronger muscles help keep joint and other pains away. When ever I build that muscle group back up, that pain is gone for quite a while.
As I get older and do less activity, I've found that my muscle mass is diminishing in some areas. And those tend to be areas that I'll have a corresponding issue with on the bike. Thankfully, I've been able to correct it with irregular amounts of resistance type exercise of those muscle groups. But at my current age of 66 and retired, I'm even more than ever looking like I'm going to have to pick a gym and start going there 3 days a week.
You and any other old person should also consider if loss of muscle mass as we age is a possible cause for pains you have on the bike. And if the answer is yes, then do something about it. Exercise those muscle groups!
Riding the bike really only exercises the heart muscle. And maybe the legs.