Even though I don't use the retail/restaurant system for it's original purposes because it was a bit disappointing I have found other uses for it in my game.
Number 1: Separate household funds
What I like to do in my game is have separate household funds for my sims so they can save up for things. You can do this by purchasing an empty lot as retail store (or a restaurant if you don't have gtw). Then name the lot the something like (sim name)'s account. Buying the lot will cost money but you can cheat the money back or pretend it's the fee for opening the account. Then when your sim gets paid you can just transfer the money from the main household funds.
Number 2: Owning multiple homes
If you ever have really rich sims and envision them having a second home, you can buy one as a retail store or restaurant, and if you don't place the required objects it will be classed as a residential lot. Easy!
Number 3: Moving sims out but still controlling them
If you play legacies this may be useful to do if you want to move a sim out but don't want to lose complete control of a sim and not get notifications for them. You can just have your sim live at the second location and when you want to go back to the main lot you can click another sim in the household at the main lot and select the option switch control to (sim name).]
hope these were helpful and I explained them properly lol