Most of the time when people do this, they're open to accepting an offer if it turned out to be really great. They just know that such an offer from a particular company is really unlikely.

I don't see a big problem with it. While it may 'waste' some time on the company's part, it also sends a signal of, "hey, you could get some of these really high quality engineers if you were willing to [pay more/offer more vacation/offer remote work/etc.]".

Now, if you're unwilling to accept an offer from a particular company even if their terms blow you away, then yeah, that's a dick move.