I personally think the majority of the non-elite dopers will be older guys. I'm sure there's some OTQ-level people who juice, but I can't imagine too many of them knowing the risk/reward. The biggest demographic is probably the competitive 40–60 year old crowd. I know a guy, in his late 50s or early 60s, always been reasonably fit but never crazy fit, runs NYC almost every year. I think he cracked 3:00 in the marathon a few decades ago. Anyway, he recently went from "good looking fit grandpa" to "massive bulging veins in his biceps" in like a year and it's hard not to be very suspicious, especially considering he was never into strength training. Dude pulled a Jeff Bezos.
Related, I believe West Side Runners in NYC had some sub-elite guys get popped a while ago. Their circumstances are very different from most hobby joggers like me, many were racing for their livelihoods and sending money back to their home countries. So they'd go out and win competitive but not-too-competitive local races almost every weekend.