The other replies make some good points about why people like squash, but here's more:

1) You only need one other person to get a high-intensity workout. This is much easier than reliably mustering 22 men for a soccer game, or 10 for basketball.

2) It's a medium-impact, mostly-non-contact sport that doesn't involve jumping, but does involve a lot of lunging motions. This means it causes waaaaay fewer injuries than e.g. basketball (esp. serious knee injuries), and also promotes flexibility in the hips and knees. That flexibility turns out to be important for general well-being and mobility as you get older.

3) You don't need a lot of gear, just the gym shoes and gym clothes you already have, plus a racquet and a 2 dollar ball. You can get a 20 dollar racquet or a 800 dollar racquet, depending on if you're a cheapskate or a gear nerd, or anything in between.

4) You can play it indoors, with or without the cooperation of the weather.

I have played squash and my wife is an orthopaedic surgeon. Per her, and from my experience, I can say that any serious squash is not easy on the joints (knees, ankles, thighs, hamstring, etc). I have done swimming, field-hockey, cricket and table-tennis (though not as a pro) and I can say this with a lot of confidence that Squash was the most intense even its in amateur/basic form.

But if you're in it for fun e.g. play it 3 times a week for like 20 mins then maybe yes, but definitely check this with your doctor.

Please buy goggles too!

Its still pretty bad sport re long term health, joints don't like this kind of stress, plus tripping/hitting walls. Its cheap on equipment, that's true. Its pretty engaging, but I would still recommend to anybody bouldering (no partner needed) or gym/rock climbing. From my personal experience, better in every possible way

It is a very "efficient" sport in terms of calories burned per unit time. And great fun too. This makes it popular with busy people - tech, finance - who are likely to pick a sport based on an excel sheet analysis :)

But I wish that the squash courts in US are not located within expensive athletic clubs, like in UK or Pakistan. That would've popularized the amazing sport more here in US.

It's efficient space-wise as well - a city-centre gym can fit squash courts more easily than tennis/volleyball/basketball.

I didn't believe this about basketball, since it accommodates 5x as many players, but it's true: a squash court is 62 sqm and a basketball court is 420 sqm. OK, you can't tile squash courts with no wasted space between, but you normally need some space out of bounds of the basketball court too.

It's a class-segregated sport in the US (not sure about elsewhere). This is called out in the tongue-in-cheek-but-mostly-accurate Official Preppy Handbook. For some reason it is "higher class" than racquetball, and, sure enough, racquetball courts are much easier to find in non-rich areas. Perhaps this is a case where the general principal from the same book holds true: the smaller the ball, the more Prep the sport (squash balls are smaller than those for racquetball).

Yeah, it's a problem. It just reflects the people who are where the playing courts are in the US. If there were courts anywhere but at wealthy coastal universities, more people might be into it. It's lots of fun.

When I was in England, it was so much more a common sport. I joined a club where there was even a bar serving food and booze in the middle of the squash court wings. I guess drinking is part of sport over there.

My interpretation is that the sport had a huge peak of interest in the 70s and that generation of players dominate the dwindling number of new players

I think it was the Economist who described squash as "chess at 100 miles-an-hour". If I had to guess techies like the speed and thinking that goes into it, and the intense cardio helps focus at work.

Because you typically play with one other person (unless you're doing doubles), it can be another way of casual networking.

It's easy and fun plus a fantastic workout.

Until you get hit in the eye with a ball. (Yes, I foolishly used to play without eye protection)

It is? I thought it an old fashion thing? My partner was massively into it and even played competitively back in the 00s.

It's a logistically simple ubiquitous sport that is weather-independent. What else would they play, if they want a sport? The only thing simpler is running.