I've always thought of it in terms of the "heroe's journey" trope, as played out through mechanical progression. At early levels, you are vulnerable and weak because that sort of echoes the feel of the fantasy heroes of old, where you start out from your farmhouse or moisture farm or whatever and really have no idea what's going on or the kinds of threats you'll be going up against.
Then you level up once or twice, and you start getting tough enough to actually go toe-to-toe with threats, gaining new powers or tactical options which also make you more capable and increase your options in a given confrontation. So, you've responded to the call and have now begun moving towards your goal consciously.
By the mid-levels, you become an unstoppable powerhouse compared to most people you've ever met, but the opposition is correspondingly powerful and eventually mythic in scope, mirroring the highest pitch of heroic adventures where you are blowing up the Death Star, Fighting whole trucks of Nazis, and defending Helm's Deep and having a blast doing it.
So I find the mechanical pacing to be one of the really charming things about D&D style TTRPGs!