You and I might do it as a connected reflex between the space key and ctrl key to always get a higher chance of reaching a ledge with no drawbacks, but it makes no digetic sense. People in real life don’t do a squat mid-air if their only intention is to step up to a higher object.
FPSes of both the realistic and cartoony variety have been introducing step-ups as a way to simplify movement for a long time. Examples: DOOM 2016, Deep Rock Galactic. It also means that they can connect other important game functionality to the Crouch button if that keybind just doesn’t do much for the intended gameplay.
That’s the thing, I was careful about my wording; “if their only intention is to step up to a higher object”. If I tell someone to get on top of a cement block, their impulse won’t be to do a parkour jump where they’re tucking their legs, they’ll likely use their hands to lift themselves up. They wouldn’t even think of their action as a “jump”. When people press the spacebar in a video game, the intent is clearly to get higher onto the thing in front of them, it’s just most games choose not to express the particular actions a human does to do that (much like how we dropped Tomb Raider’s approach of manually holding a button to grab onto ledges)
In DRG, the way they differentiate intention is with the direction you’re looking - you can only mantle onto platforms you’re looking towards. So, you wouldn’t get many occasions where you’re dodging sideways and accidentally get on a platform.
In DOOM Eternal, they got rid of crouch, and put the grenade launcher on there. G was changed to toggle between your two grenade types. In Deep Rock Galactic, Ctrl uses the player’s laser pointer, a tool for communicating to teammates that doesn’t really impact gameplay. Having a free keybind offers a number of ways to enhance or simplify the game; if they wanted to go for simple measures, it could be a context-sensitive VO button, like spotting out enemy players.