I recently did a few interviews & was shocked at how often I would complete an entire loop (coffee chat, tech screen, full-day 'onsite') only to be completely ghosted. I'm totally fine with rejection, I don't think I've ever done better than 50/50 for an offer, but it's super unprofessional to just ghost someone who's given you 5+ hours.
It's not that hard to just send a "thanks but no thanks" email.
To name names: Flymachine.io, Boulevard, and Pepper.