While I don't use mine often I won't be without one either. I can use trainers in a pinch, and have, since mine is being totally redone.
But not having a trailer when you have horses is a nightmare. We live in area where the nearest good equine vet is 50 miles one way. That is 100 dollar farm call at current rates. And the other vets are even further. And trying to find a trailer to borrow is a nightmare. And there are no places that rent them that I have found and that is even in the 3 big cities within 90 minutes one way.
Which means, even if I could find one in those cities? I would be out the drive to pick it up, then have to come back and load horses, and then afterwards drive back down there...nope.
I too rarely lend my things, and definitely won't when my "new" trailer comes home. I do plan on getting carport to put it under to protect it.
Horses make me a better person.