DC and Marvel are different cases.
DC is much older, being pretty much the sole survivor of the Golden Age of comics. As other comics companies from that era – such as Charlton Comics, Fawcett Comics, and Quality Comics – eventually went under, DC bought a lot of their properties. Marvel, or Atlas as it was known then was selling comics, and a few characters trace their origins back to that period, but Captain America is pretty much the only character widely remembered.
In the Golden Age of comics, comics were 100% avowedly for kids. You had major reader turn over, with readers in a very narrow window of childhood. There was no such thing as universe or character continuity, because most readers would not remember what happened a year or two earlier. A lot of stories got told multiple times (new art, new writing, but same premise). Marvel largely ignored their golden age characters and recycled concepts – the Destroyer, the Vision, the Human Torch – later with no reference to the earlier characters.
The Silver Age was for the Baby Boomer generation, and a lot of the tone was driven by Marvel, which was the first to really push the notion of a single living, breathing universe with all of their characters. (So much so that it can be easy to forget some titles like the Eternals had deliberate “outs” so they could claim it was an un-connected universe if fans didn’t care for it.)
DC jumped on this bandwagon, and eventually settled on the notion of two parallel universes. All the goofy golden age stuff was on Earth Two. Earth One is where the stuff is happening now. So that was less an explicit reboot than “let’s just forget about all this stuff back here.” Over the years, DC has had a few reboots, but they’ve been accelerating. Ages ago you had Crisis on Two Earths; more recently you had Crisis on Infinite Earths/the new 52.
But DC also had a lot more TV/movie presence, and a lot of those introduced original ideas that made their way back to the comics (such as the character of Joker’s moll, Harley Quinn). All of them had very different markets, writers, and times. Some versions of Superman and Batman are campy. Some are dark.
DC has also had a very strong “Elseworlds” trend-cum-imprint since the late 80s or so. They were very liberal with printing limited, standalone stories about Batman vs. Predator, and Superman vs. Godzilla, and cowboy Batman, and Soviet Superman, and so on.
Batman, Superman, Flash… these are all just general concepts on which you can hang certain flavors and variations. Fans accept it, and don’t worry too much about the details. Some jokingly refer to DC as “Disregard Continuity”
