Either you haven't played or don't play competitive matches. I grew up playing tennis and now mainly play pickle amongst racket sports. I play 2-3 times a week for around 2 hours straight, and am comfortably a 3.5+ player. Even in a competitive doubles match, there is a lot of sprinting and movement (certainly not as much as tennis but still a good work out), and singles is an even bigger workout. I can play matches with players who are 20-30 years younger than me on a competitive level with the smaller court size and the fact that pickle is not purely a power game. The pros typically play a dink focused game, but most players mix it up, which also contributes to the workout aspect. And it is really fun and social.
JMHO. See you on the courts!