I've always thought that the assumption is that if a creature is not taking the hide action, they're just clunking around making no effort to be quiet. And in a magical world where invisible creatures and the invisibility spell are the known thing, hearing footsteps/the sounds of a creature but not seeing anything, like it's not some huge leap to think "hey, there's someone invisible, and they're about 10 ft to my left."
Blindsense amounts of auto-succeeding on the perception check (when the invisible creature comes within 10 ft). Everyone else would have to roll, or more likely, the creature would have to beat their passive percep.