I think that MSD would be a lot more respected if it put the student into a position (real or simulated) where they were acting as the most experienced/most responsible diver on the dive.
That would directly compete with Dive Master though which is their leadership qualification of choice so not good financial sense to them.
As much as BSAC manage to do wrong lately at least all their grades have assessments on dive leading by example, demo and repeat all the way through from ocean diver onwards.
NAUI "master diver" has similar theory to divemaster. Neither are exactly "masters". They're both relatively easy recreational qualifications at the end of the day.
The liability thing just isnt true. Im not aware of anywhere civilised that *requires* a divemaster by law. It isnt a mandatory role, you don't need one to dive and all agencies train divers to in theory be able to dive independently after certification (i dont count the scuba diver or clones in this as i dont think they're real qualifications). You're not in a commercial role, you don't need any more insurance, you're just diving. For fun. People scream libel and take it too far without ever backing it up with actual cases.