And with many specialized shops, including ours, your rental can count towards purchase. Making it a very low risk proposition. Either you love it and didn't spend any extra money to buy it, or you don't like it and you save a huge sum from not buying.
But you also have to understand that not everyone lives in a high-population area where MF rental is common/easy. Also not everyone has the appropriate insurance to rent e.g. 30k of equipment and getting one-time coverage is very cost prohibitive.
This is where we get a lot of people that fly to NYC to try the equipment out in person (I'd imagine the same is true for cities like Moscow or Berlin, but I can't speak to that). Usually when we have such a person we try to make accommodations to go "out and about" in the city with them, or set up a mini shoot at our office studio, so they can get some idea of real world shooting without having to rent or deal with insurance.