You said "when brokers offer low margins and high BPs, traders take more risks than they should.".
Traders who are experienced know that they don't have to use all the BP and those who do use it, are diversified and the higher leverage actually improves the risk metrics. It's not complicated. Forcing someone to use lower leverage implies they cannot control their risk themselves.
I don't know of any serious traders using Reg T. By default Reg T offers 2:1 leverage interday and 4:1 intraday. This is true for most brokers but you might be using something that isn't regulated the same.
