Just to be contrarian:
Do you think the market players care about protecting traders from themselves? This is the official reason for the PDT rule. I mean, the market relies on a steady stream of losers and currency created out of thin air to allow winners to win. Remember, lots of little losers are generally on the other side of your large winning trades. The two groups of losers are: other individual traders and our currency.
Large players in the markets do EVERYTHING in order to protect their competitive advantage. Back in the 'day', you had to short stocks on an uptick or zero plus tick, so most traders were prevented from taking positions at smart points when stocks fell. Sure, you could short on retracements, but everyone else was trying to do that as well (in retail trading, those of us at prop firm simply used bullets, which also generated more fees).
Another "innovation" by the big boys was the capital lockup rule at prop firms, thus reducing an individual traders' competitive advantage further. Don't like how your firm is treating you, ..tough shit your original capital is stuck here for a year.
One thought I have always had, even if it proves to be ultimately erroneous in action, is that the 25K pdt rule was to prevent the unlikely event that smart guys with discipline could day trade their way up from nearly zero capital to something like taking a large piece of the pie from others. The PDT rule, even though 25K in today's dollars is probably the equivalent of 5k when I started, just from reading the threads on this, is a significant barriers to 90% of all traders who want to start. A few of these traders would eventually take a piece of the pie in time.
Most all day traders lose, and lose their capital quickly. So I can see the merits of the PDT rule from the 'official' story. While it is unlikely that being able to day trade on small funds can create big winners in the markets, beyond fixed costs, a disciplined trader with a reasonable methodology can run up an account from a small amount. In a weird perhaps unprobable sense, I think this is the establishments biggest fear, and most legislation that prevents trader freedoms can be looked at through this lens and not be completely of base.