Except for people on minimum wage, I don't agree that those really count as wage theft.
Say you forced employers to account for the time closing and locking the store or to compensate people for spending hours away from their family. What would happen is that the hourly salary would drop to account for that, since in reality the workers are already taking those into account (as you say, they already consider it normal - and therefore expect it) when they accept the job.
Except for minimum wage workers, they are just examples where the actual contract is an informal agreement, and not the piece of paper that was signed.
Of course they should get paid for locking the doors, minimum wage or not. You claim hourly salary would drop, but at places that pay people correctly, it doesn't. Say a store is open from 10 am to 10pm. You hire one person to work 8 hours in the middle of the day. They come in say at noon, work 8 hours and leave at 8. Someone else comes in at 2 and works till closing, say 10:30. They do an extra half hour to clean up and lock up, so they should get paid less?
I suppose in a shop where workers have a fixed schedule (e.g. noon to 8pm, 2pm to 10pm) that might happen, but the vast majority of retail jobs aren't like that.
According to surveys, besides personal experience, something like 80%+ of retail jobs have at least shifts, if not full on-demand schedules, so there's no set of workers that always close the shop and others that don't - they all do, some of the days.
I've often thought the same about unpaid overtime for salary IT employees -- in some high profile cases where a company was successfully sued for unpaid overtime, the affected employees were reclassified as hourly and given a pay adjustment that resulted 20% or lower than their previous pay (although their paychecks ended up being about the same, because they could then earn overtime).
That makes some sense, superficially. But you forget that the workers who enter into a contract have a reasonable expectation that the employer is abiding by laws and will pay them minimum wage.
The minimum wage on the other hand is meant to make someone able to feed themselves and maybe even a family. Especially when holding multiple jobs, such unpaid overtime, even just opening/closing a shop can cut into that ability in a serious manner.
Say you forced employers to account for the time closing and locking the store or to compensate people for spending hours away from their family. What would happen is that the hourly salary would drop to account for that, since in reality the workers are already taking those into account (as you say, they already consider it normal - and therefore expect it) when they accept the job.
Except for minimum wage workers, they are just examples where the actual contract is an informal agreement, and not the piece of paper that was signed.