Because they only made a fraction as many in .22 as in the larger calibers.

S&W .22's, (along with any quality .22's). were always a hard sell to the average gun buyer. They actually listed for more than their centerfire counterparts. Joe Gunbuyer, reckoning that if the ammo was cheap, the gun should be cheap as well, usually wouldn't spring for what they cost.

It's a pity, as they missed out on the K-22's, Kit Guns, etc., that were worth every penny they cost.