I think it's because the K-22 is in a class by it's self. Lots of folks made 22 revolvers, the K-22's and model 17's were just the creme of the crop, very desirable for the craftsmanship and shootability.

You may mention the Colt 22's and to that I say they were scarce according to my observation and too pricy as compared to the S&W models.