How would they know if the ex-tenant or their crazy girlfriend or mother or whoever doesn't have a duplicate key? Most places would have a policy to re-key the locks anytime someone moves out. The landlord would be failing to take ordinary precautions for the new tenant's safety if someone could easily enter the apartment with an old duplicate key.
That cost doesn't result from the tenant neglecting to do something, so they can't charge him for it.
All that depends on the laws of the state. We can charge for keys in our state. So I always ask the tenants if they would like new locks and the cost of putting in new locks. Most of the time they decline but sometimes they want to pay so we make them pay for it.
For my units, I use Defiant locksets which is Home Depot's in house brand. Can't really rekey them. One employee said "Defiant? You mind as well leave your doors open.". But I like them because they're cheap. Another landlord likes them because they're easy to drill out although I haven't had to do that yet.