One thing hosts need to be aware of is that, believe it or not, not everyone uses a smart phone and apps. Or their phone could be dead, out of charge. If a guest who can't self-check-in easily to a place where the host doesn't greet them, that would be a big problem.
Modern technology can be great, but a host can't just assume that every guest will be able to deal with it.
Personally, were I a guest, I would want a key lockbox instead, that I was sent the code to. That also would eliminate the possibility that the batteries could be dead and a smartlock then not function.
Smooth check-in can set the mood for a entire stay. If a guest stood out on the street for a hour trying to get the lock to work, messaging the host, etc. they can be a lot more critical of other things about their stay than they would have been otherwise.
