BambuLab wants to be the Apple of 3D-printing. So they simplified and decided the factory bed level with auto bed leveling/compensation is good enough for the user.
On high end printers there is just no need to level them. The factory does it and the bed won't move at all due to the excellent mechanical designs.
Everything else? They have it to level the corners of the bed and use automatic bed leveling/correction to get it perfect and adjust for build plate imperfections.
There is one system that does level the bed but doesn't need the knobs as each of the three mounting points is connected to an independent z-axis (kinematic bed): https://www.youtube.com/watch?v=bgkK7Fez8VU