Here in Czech Republic, Poland, Slovakia, etc is renting a car worth it if you do it maybe once a year, otherwise owning a universal large car is much cheaper. I rented a van for 2 weeks and realized I could have bought a used one for just 1.5x the rental+insurance price.
Here are much smaller (10x and smaller) taxes on vehicles, that is probably the reason.
Any risk analyst could tell you all the factors you don't take into account when you do a simple comparison of renting a new, cared-for, insured vehicle for which someone else is responsible vs. the crapshoot of buying something second-hand, which you now have to take on, whatever goes wrong.
I also doubt you are taking fuel into account with this comparison, which was the primary source of savings mentioned when you own a small car and rent a truck as needed.
Most people here drive Skoda Octavia which is one of the most fuel conservative vehicles on the market, worldwide. Having a smaller car brings no measurable gains.
Here are much smaller (10x and smaller) taxes on vehicles, that is probably the reason.