Well yeah, because running an exit node in the US is "probably legal but there's precedent for still getting arrested and having your stuff seized." I can't imagine very many normal people are willing to paint a target on their backs like this.

In many countries, running an exit node is a very fast way to have cop knocking at your door and seizing all your stuff. To run a tor exit node, you either have to try your best to stay anonymous, preferably be based in a country who don't care at all about cyber crime, and run them on a dodgy hosting provider who dgaf. Or you have to create a legal entity, either a non-profit or a company, depending on the country register as a hosting provider (so that you are not consider legally responsible for what comes out of your server if you abide by some rules), and you will still have to respond pretty fast to any police inquiry.

If anything, it's a miracle that there is 3000 of them. Although you can safely assume that a good portion of them (if not the majority) are operated by state intelligence services, cybersecurity companies and bad actor, who will log everything that pass through their node (and might be able to decrypt them one day).

It's insanely few, but also isn't that possibly an advantage? When lots of people's transfers are intermingled that means the possibility of separating out one person's traffic from the rest is harder.

Because running one will get your machine blamed for any illegal activities that Tor users are up to. I ran one for whole 2 weeks, before my hosting provider just told me "pls stop".

Also depending on country you might be accused by aiding them, and it would be upon you to explain the court you have no control who uses the exit node nor their ID

So one person single-handedly knocked out 10% of the entire Tor exit network over an SSH port redirection?