Just a theory based on basic understanding of physics and matter, but... You'd break a lot more hardware and risk damaging expensive trucks instead pf cheap bolts. There's a reasoning is that baseplate holes are a size bigger than they need to be. Even tightened down the baseplate isn't rigidly locked into place, there's potential for a minute amount of movement under pressure. Say your board shoots out straight into a curb at high speed- If there was zero give then it's more likely to bend the bolt, in effect damaging the threads. Maybe not noticeable at first with time it would get less and less secure. Same with deck holes, both of them slightly bigger than bolts, and both can reduce force of impact.
Also, if you break your bolt inside the baseplate you'd probably need to drill it out, also likely to damage threads unless you can hold a drill with surgical precision (such a small bolt would be hard to tap/thread to unscrew it).
And, no locking system is perfect. If it's getting beat around all the time like a skateboard does, it's gonna get less effective.
In the end, you'd have a more expensive product that's more prone to damage and thus needs to be replaced more often.
I'm sure plenty of companies have experimented with this, it's not like a ground breaking epiphany, and there's a reason a company like Tensor or something didn't already revolutionize skateboard truck design with this idea.
About reducing the amount of tools needed: You'd still need a screwdriver. T-Tool + screwdriver = 2 tools needed to do everything you need on a skateboard now, and 2 tools needed if baseplates were threaded. Hmmmm...