This is a little bit of a tangent, but here goes...
Last June we were staying at the Hilton across the street from DTD, and we grabbed a ride to DTD, via SSR, on Disney buses to get from MK to our hotel. So, I guess we're part of the problem the OP brought up.
But we had a reason: we had learned over the course of several days that the bus to the Hilton (shared with many other hotels) was very crowded and sometimes much more infrequent than it claimed to be. (One bus that was supposed to depart every 30 mins had a 70 minute gap one day, while we waited in the the sun.) Anyhow, it was a late MK night after fireworks, our 3yo daughter was dragging, it was very hot, our bus was not in sight; it occurred to me that if we could get ourselves to DTD instead, we could simply cross the street to the Hilton.
So, we hopped on a large, clean, full but not stuffed bus to SSR, immediately caught a connecting bus to DTD, and I carried my sleeping daughter across the street and home. No harm, no foul, since we had park tickets (see the quote).
But, if our appointed transportation had been better, we wouldn't have thought of this plan at all. We weren't eager to come up with a crafty transportation scheme, we simply wanted to get home.
I suggest that if Disney improves transportation to DTD, this problem goes away. As a complement, charging for DTD parking, with validation from retailers, as many have suggested above, seems like a reasonable way to mitigate abuse of the system.