This is true but as somebody sitting in a truck camper right now I'm here to say that this isn't a 100% blocker. Every camper has pros and cons. When we haul our fifth wheel it's way more work to hook that thing up because the hitch itself weighs like 300lbs - it takes like an hour to prep for hauling the 5er.
For me, a truck camper is a whole different class of animal. Unless you're driving a 3500 dually you're going to have extremely limited space inside. Tiny bathroom, tight kitchen area (somebody always has to be sitting down), climb-up-and-pray beds, extremely limited storage, high bed weights reducing your overall cargo capacity, and while people do travel with them with pets, they aren't really ideal for that... I could make a list of cons the length of my arm.
I'd still use mine for 100% of the situations that I got it for. Like this one: hunting. I can show up to any campground or parking area and know if my truck fits, my truck+camper fits (it only adds 2' to my overall length). I can show up at 11pm and go to bed immediately - no camp setup. I can pre-pack it with all my hunt gear and "just go" without having to drag duffel bags of gear and clothes between car->tent or whatever. Its tiny size makes it very efficient - I'll blow through a bottle of propane every day or so heating my 5er, but so far I'm on day 4 of a muzzleloader hunt (overnight lows averaging 19F so far) running my heat, cooking, and fridge off propane, and I haven't changed the bottle yet (probably today). And it's just enough room for person+spouse or hunter+partner.
Loading it does take some practice and effort. There's no hitch, but alignment is crucial and I need to install a 2" riser I made so the cab-over portion clear my RAM's shark-fin antenna. But we come up with little tricks like tape flags on the legs to help with alignment. You get used to it.
Truck campers are really expensive for what you get compared to other options and definitely have a list of downsides. But for a very specific thing for a very specific buyer they are 100% perfect. I'm one of those people, and would never give it up.