If you’re poor, most of those things require some non negligible percent of your income—-if only just in gas/transportation.

But more importantly they require time away from working/studying/optimizing for bank account balance.

No doubt, those things are great. But if the reason you're doing them is because you refuse to spend the money you do have, then those start to feel pretty finite. I think it's particularly obvious during the pandemic. The first 5 times you go for a walk are great, and then you propose getting some food in the park to change it up a bit. Maybe you need to rent a car or get a minimum kind of shoe to get to different hiking spots, and your miserly friend doesn't join just because they'd rather excessively save their money. Or you don't live somewhere with hiking, or you just want to sip coffee at a cafe but they won't buy anything. Or you want to invite them to a party but they choose to never bring anything to drink or eat. It's just kinda lame.

Again, this is more about choice rather than necessity. Carries a different vibe if you're trying to do whatever you can reasonably afford, and that may mean not spending anything extra. Good friends will accommodate, but if it's obvious you're making over 100k a year (without significant dependents etc.) and won't split gas, well that doesn't lend itself well to collaborative fun times.

Edit: Also, I don't mean to suggest saving money in general is inherently bad. Obviously not. But you need to be able to find that balance. I personally tend to place higher value on the chance to hang out or have a drink than having 20 more dollars in the bank. But many drinks over many weekends maybe not as much.

I find I do that just great with friends and no money, until I want to do it far away

This is hacker news where everyone values their time at at least $100/hr. If you're socializing you, at the very least, aren't working.

People like to drive outside the city to hike, travel, go to restaurants, movies, bars, ballgames, museums etc...

You don’t need to spend a huge amount on social stuff, but if you are only willing to do completely free activities, you are vastly limiting your social circle.

Decently socializing with me would require a modicum of effort on each of our parts to engage in stuff. If the activities tend to cost something, and you choose only to conserve your money, then you wouldn't really be doing that would you?

If all the activities were costly, and I didn't put effort in to do other cheaper/free stuff to socialize with you, then I'd be the asshole.