When it comes to economics, there are different notions of rationality. According to a popular one, if offered double or nothing on all your wealth, with a 51% chance of winning, you should take it. This completely ignores everything from risk tolerance to diminishing marginal utility, but it's simple to model. Actual people can be counted on to fall short of this version of rationality, and that's probably a good thing.
Some forms of insurance are practically a forced move, others are so overpriced that it's cheaper to self-insure. So, for example, it hardly ever pays get an extended warranty on consumer electronics, but you'd be a fool not to insure your house and car; unless you had enough cash sitting around to replace them without too much pain, and perhaps even then. I suspect that Elon still insures his mansion(s); maybe he's irrational by some definition.
There's definitely a place for debt, particularly for large items that you want to be able to use today, not wait years until you've saved up for. The interest has to be weighed against how much you'd spend on the alternative in the interim. So I've certainly taken on debt for houses and cars, for example. But paying off or avoiding debt gives guaranteed returns that are hard to match. I've bought houses and cars for cash, when it was possible, and I don't regret it.
I've seen people carrying substantial credit card debt looking for investment advice, oblivious to the sure-fire "investment" they have available to them. This isn't rational, by any definition, but it sure is common. Perhaps I'm erring in the opposite direction. Perhaps I could squeeze my capital a bit harder and eke out a higher return. Then again, we're in the middle of a catastrophe, and I'm still sleeping soundly at night while planning on some big expenses.
So, to bring this back to the topic at hand, I'm paying cash on my Tesla, whenever it actually gets delivered. I had accumulated some cars over the years and recently sold them, so you could consider this a side-grade. Maybe I could instead speculate on the market once I think it's hit rock bottom. Maybe I could win the lottery. Or maybe I could just drive my Tesla and be happy. It's irrational, but what can you expect from a chimp?