I own a trailer because even though I rarely need it, renting is too difficult. I did rent a trailer a couple times. However finding one that was available and fit my needs is harder than you would think. There are many different types of trailers, each serving a different purpose, and most won't work for my purpose. When I need one is also the weekend others need one and so it is highly likely to be unavailable because someone else has it.

I've tried to make your "rent when you need it" for those rare uses. However every time I do I realize that the cost of a rental is very high, and most rentals have restrictions such that I can't even use it for what I wanted. I've been lucky to never arrive to find my reserved vehicle isn't there, but that has happened to many people I know as well (leaving them at an airport with no way to get around)

I collect antique tractors, this is one of those rare niches that make me unusual. Having to have a trailer for them to get to shows is part of the costs (and fun). To ensure I can do what I want when I want I have to own a truck and trailer.

While you are correct the cars are depreciating assets, so it life. I have more than enough money for the basics: I don't need more appreciating assets. Most of my money is reserved for things that bring me happiness, and I don't care (nor should I care!) if it is a good economic investment. Investing everything to grow a number on paper seems like a boring wasted life to me (but this is just me, if your happiness is that number then by all means invest more)