I've considered one on a few occasions, but one concern is if you are away then if you want to go anywhere you have to pack everything, up whereas a caravan you can go off in the car. But horses for courses
Which is exactly what endears caravanners to the locals. Not.
When I'm where I'm going I switch off the engine, pull the lever to rotate the captains chair to face "indoors" and crack open a beer. No faffing about unhitching, setting feet, etc, and when I'm sober I'm ready to leave instantly - lock the drivers seat, turn the key, and wave adios to Terry and June as they're still messing about with the Wally Wagon. I've watched some caravanners take an hour to get sorted, hitched, redistribute the load to set a decent noseweight and on their way, by which time i'm half way home.
Plus there are targets of opportnuinty not open to caravanners. Highland layby's, friendly pubs (the Pilot Inn at Dungeness lets visitors stay in a camper/motorhome for free so long as they buy an evening meal, for example - many remote country pubs permit this), remote spots that simply aren't reasonably available for a caravan. And they're safer on the open road. On a long journey you can pull over for a break, rest or spot of lunch and you're instantly all set.
The only downside for me is the cost of taxing, insuring and maintaining another vehicle, but thats's negligible and certainly a lot cheaper than having to buy a new caravan because someone has nicked it.