That's always been as effective a safeguard as "Do Not Copy This File." This app doesn't meaningfully change the risks associated with that.
Physical possession of a key for more than 5 seconds means you own the lock it is associated with, at will. (Or, these days, a photograph will work.) The Grand Old Order of Locksmiths likes to pretend there's a long tradition of professional norms which makes this impossible, and thus it is safe to give someone a key but treat their access to the lock as revocable, but that's mostly hokum. It's a shared secret between the key and the lock which happens to have a physical encoding. If somebody sees the encoding, the secret isn't a secret anymore. The mystique of the locksmith is that the encoding is more esoteric than "this is my password", but that's not actually a very strong security guarantee if you expose it to adversarial action.
Relatedly, most locks can be defeated by a bright 8 year old with tools which cost less than $100. This is also one of the things which the Grand Old Order of Locksmiths would have you believe is totally unpossible, because that would require someone to have illegal possession of lockpicking tools and forbidden knowledge, like a) a can of compressed air and b) a 46-second Youtube video.
This is all true, but the Grand Old Order of Locksmiths hasn't evolved this line of patter for no reason. Many people of my acquaintance are terrified of the possibility of burglars, even though home intrusions are very rare. Boosting people's confidence meaningfully improves their lives, even if 50% of the confidence boost is pure placebo effect.
And physical locks do accomplish some things. They often require aspiring thieves to choose between speed and subtlety: Kicking open a door is fast but loud, picking a deadbolt is quieter but consumes a bit of time, and obviously both are slower and more obvious than opening an unlocked door.
Physical locks protect against "misunderstandings". If you pass through a locked door and you don't have a key, you'll have a hard time convincing a cop or a judge that you were just making a mistake, or that "I saw the door standing open and was trying to investigate."
Similarly, the "do not copy this key" message is not intended to be binding on locksmiths. It's a tiny contract between the landlord and the tenant, so if the tenant makes fifty copies of the key and hands them out at local bars, the landlord has clearer grounds for complaint.
Finally, locks guard against crimes of opportunity. Not all of the world's aspiring thieves bother to learn lockpicking. Not all of them are sober enough to be very smart. And, as criminologists are fond of pointing out, a large percentage of crimes are committed by people the victim already knows, and there's a big social and psychological gap between "wandering into my cousin's house, seeing fifty bucks, and pocketing it" and "breaking down my cousin's door to look for fifty bucks."
I guess the remaining question is if a member of the "Grand Old Order of Locksmiths" would normally generate a new key from an image of a key. The KeyMe people think they would if they were "following instructions we display on your phone". So it sounds like the process has been made simpler and is now being encouraged.
Physical possession of a key for more than 5 seconds means you own the lock it is associated with, at will. (Or, these days, a photograph will work.) The Grand Old Order of Locksmiths likes to pretend there's a long tradition of professional norms which makes this impossible, and thus it is safe to give someone a key but treat their access to the lock as revocable, but that's mostly hokum. It's a shared secret between the key and the lock which happens to have a physical encoding. If somebody sees the encoding, the secret isn't a secret anymore. The mystique of the locksmith is that the encoding is more esoteric than "this is my password", but that's not actually a very strong security guarantee if you expose it to adversarial action.
Relatedly, most locks can be defeated by a bright 8 year old with tools which cost less than $100. This is also one of the things which the Grand Old Order of Locksmiths would have you believe is totally unpossible, because that would require someone to have illegal possession of lockpicking tools and forbidden knowledge, like a) a can of compressed air and b) a 46-second Youtube video.