In the Marvel universe, gamma radiation gives you super powers because the Celestials tinkered with human evolution.
My favorite head canon for why no one ages in Marvel is the Franklin Richards doesn't want them to. When Marvel started in the sixties it ran in real time. Peter Parker was in high school for four years or whatever of our time, then went to college. No one knew they were creating cultural touchstones so this didn't seem like a bad idea. Franklin Richards is the most powerful earthbound being in Marvel. He can control reality. He was born in 1968 right around the introduction of "Marvel Time." The theory goes that Franklin doesn't want to grow up or for his friends to age and die so he has essentially stopped time for the entire universe.
As for DC, there's a crisis that resets time like every two weeks.
One of my buds is a huge DC fan. When I asked him how he felt about this latest reboot, his exact words were "I am so relieved." I don't read DC, so I wouldn't know, but apparently for die hard fans, it was that rough.
Ah. Yeah. That would make sense then. Have you read much of it? What's your opinion on it?
Most of my DC knowledge comes from the '90s Timmverse and then what I pick up here and there through conversations. I know DC has actually put out some good stories throughout the decades, but I just don't find a lot of their heroes compelling. I was always more into Marvel out of the big two but didn't even read them that much because I hate major events and crossovers which they seem to do every few months. So when Valiant resurfaced, I jumped in feet first since day one and haven't regretted it. They're doing a great job in my opinion.
I don't read any comics anymore but I like to keep up on what's going on. They folded the Watchmen into DC proper so that's pretty shitty but the overall reaction is positive. I recommend NerdSync on YouTube. I watch a few other channels but they're the best. It's hard to explain on my phone what they do but it's not recaps