It's the other way around - it's not that the incentive is there, it's that there is a lack of disincentive. Thieves know that there is literally no enforcement whatsoever and police is far too overworked to deal with trivial matters like armed robberies. I know someone whose house was broken into while they were inside, the thieves still took the keys and left with the car, the Manchester police didn't even send anyone out to inspect the scene, take fingerprints or anything. They were told to report it with their insurance company and that's it. My sister's house was broken into 3(!!!!!) Times when she lived in Manchester last year, she sent the police CCTV footage of the criminals and everything, they never came out and said thanks for the footage but they are all wearing balaclavas so it doesn't help in any way.
If you were a thief why wouldn't you break in if you knew that's the level of enforcement.
Most car thieves would not dream of upgrading to randomly breaking into a house in the US as there would be a non-trivial probability of meeting a resident with a shotgun.
So I'm actually kinda surprised upon looking this up - yes UK has a higher rate of burglaries per capita than US[0], but not that much higher - 527 vs 617. Despite owning literally 30x times more guns per capita than UK(120 vs 4)[1], US is still rating pretty badly on global burglary index. I suspect it's just not as much of a detterent as people think it is.
2) "Number of burglaries" is different from "Will upgrade from car theft to robbery".
Burglars and car thieves in the US are generally trying to make sure that nobody is around and would generally find a different target if that wasn't the case.
Few would upgrade to robbery as that very much would get the attention of the authorities in the US.
If you were a thief why wouldn't you break in if you knew that's the level of enforcement.