Uber was once illegal everywhere. So were horseless carriages.
One is that an Uber rider is never put on a list of "can't ever ride on other services again", whereas if you try to sell a house that has unlicensed plumbing or electrical work done, it will show up on inspection and any smart buyer will walk (or run) away. Tons of real estate deals fall through because the seller did shoddy work like this and it will demonstrably reduce the value of your property because it's only worth what people are willing to pay.
This is also true for when you want an actual contractor to come work on your house. If a licensed contractor sees that you're trying to fix unlicensed work, they too will run away because they don't want to inherit the liability. I think the very red-tape nature of contracting work will be one of the things that protects it from this idiocy.
First, there's quite a lot of unlicensed work that is entirely legal in many places, and a lot of it is fairly common work -- replacing or repairing fixtures, for instance.
Second, there's no "list of unlicensed work" either -- sellers are required to disclose unpermitted work that they're aware of, but as you can imagine, compliance here is sometimes hard to enforce, as sellers often either don't know and minor work might not even be visible for a buyer to question. Yes, if you add on an addition or finish a basement without pulling permits, this is something that is more obvious. If a seller replaced a pipe in a wall, who is going to know?
Third, it depends on the property. You wouldn't want unpermitted work on a premium home in a premium neighborhood. But if you go shopping for a deal on a starter home in a rural area? Much of the inventory will have unpermitted work, there may be zero local enforcement, and the buyer will likely be planning on doing their own unpermitted work :)
Home improvement stores really wouldn't exist in the way that we know them if everything needed a permit.
> If a licensed contractor sees that you're trying to fix unlicensed work, they too will run away because they don't want to inherit the liability.
Many will be hesitant to fix shoddy work, but most will be fine with replacing it.