I don't know where you live so I can't talk to your experience, but where I live, if I want to rent a car for a week trip I'm driving at least 30 minutes one way, spending an hour getting the car, and paying about $1,000. If I want to rent a truck for towing (we tried this for like a year, for ~3 uses that year) we have to drive 45 minutes, it seems to take them about 2 hours to do the paperwork if we're lucky - we've waited 4 hours or more before, and we paid $350 for a weekend because they couldn't rent it for one day for Saturday because they were closed on Sunday, but charged for that day anyway. Then we got to spend another 1.5 hours driving there and back again to drop it off, 40 minutes doing paperwork.

This is a plausible PITA, stress and annoyance once every 5 years or so, but for multiple times a year, plus all the "we just WILL NOT use a truck and make due with a less suited tow vehicle and light trailer" which is more like 12 times a year, we broke down and bought a used truck.

You see - people don't buy cars just for dollars and cents, they also buy it for value, and in a lot of cases, that's paying slightly more for the ease and convenience of jumping into said car and doing what they need to do right now, rather than with days of planning.