Why does society assume barriers for the older generations?

Let me explain

I am in my late 30s currently, solid foundation to life, house wife kids all that stuff.

A couple years ago in my mid 30s I started riding motorcycles, sport bikes specifically, and it has profoundly changed my life for the better.

Last year I figured well I already ride sport bikes I may as well try the dirt, so I started riding dirt bikes as well.

However everyone I discuss these hobbies with, the automatic default answer is “aren’t you too old for that?” - like they automatically assume that a sport bike rider must be 18-22 years old , or that I’m wayyy too old to be riding dirtbikes

How did we get the notion that at some predetermined age your no longer allowed to have any even remotely risky hobbies and your obligated to “play it safe” until you eventually die?