It's all about convenience, like most things in life. How many times per year do you need to go through the hassle & headache of renting a vehicle before it makes more sense to just buy one?

1% of 365 is still nearly once a quarter. That would be enough for me.

Yeah but then you can't put a snorkel on it and extraction boards and expedition gas cans so you can advertise how adventurous you are in your spare time.