Yes instead of Sig 522, S&W MP15-5, Colt, or Rugar? I have a PLR16 and I would like to get a .22LR for my kids. I like the weight 4.0 lbs. The lightest of the above is 5 lbs (S&W). With 6 position stock would fit any size body. So why should I buy SU22?
Maybe because of the availability of Black Dog magazines and an integral rail? (putting a rail on my 10/22 was a job for a gunsmith because of the soft metal screws Ruger installed where the rail is supposed to go)
The SU-22's shape and control surfaces would work well as a cheap .22 training rifle as long as your go-to gun was an AR or SU-16.
Those are my best guess justifications. I suppose the light weight and ease of storage may be convenient as well.
I got the S&W 15-22 for Christmas and on my second trip to the range I got the notorious explosion in the chamber which broke the extractor. So I had to send my new toy back to S&W. I have been back to shoot it since then and have had no more problems but I kinda wish I had gotten the su22 instead. I think I'm just growing very fond of all kel-tec products.