The point being, why would anybody put money down on any car really, when it's a rather significant monetary investment not to be delivered for quite a while.
I'm thinking about getting a second car for my family. I don't need it immediately. A Model 3 sounds like it would be perfect for the job. I put $1,000 down to reserve one just in case. If I decide I don't want it, I'll get my money back. I'll miss out on maybe $15 of interest on that money in the intervening time, big deal.
We've not seen it to this extent in the "affordable" scene, but even if you flip it, there's probably enough market demand to be able to wipe your face on the deal if you did want to chase the new shiny thing announced in the meantime (which may or may not have extended build times too).
That being said, I'm with a lot of people here that aren't new car buyers - I know you need new car buyers to have a used car market, but I'm not tuned into the mentality of it all.
Mass-market cars on the other hand depreciate as soon as the key is turned. So not only dp depositors lose interest on that $1000 but they also lose in depreciation.