Honestly my personal theory as to why the ARMS League Association made Springtron based on Spring Man is that he probably caused the least trouble copyright and image wise in the ARMS world.
That Spring Man guy? He’s only associated with a gym, so it was pretty easy for him to give permission to have robot based off of him in every way
Ribbon Girl? Nope, she’s pretty much owned by recording studios and music companies. Plus she’s a minor so….
Master Mummy? Can we actually gain legal consent from someone who is dead.
Mechanica? Nope, she’s a minor (and is in a mech anyway)
Min Min? Mintendo depends on its owner’s good name.
Helix? We literally have five hundred clones of him in the basement.
Kid Cobra? Too deep in the snakeboarding industry.
Byte and Barq? Literally already robots. Also imitating a police officer is probably a crime.
Twintelle? Not recommended unless you’d like to be destroyed in court by every movie company she’s ever associated with.
Max Brass? Yes, there is such a thing as too much Max Brass in a room.
Lola Pop? Nonononono robot clowns is a bad idea nope nope not happening not today