The reason being is that the breech used has a bed tendency to not seat well over time, the barrel is too short of any real distance shooting & the air stripper acts like a brake & a bit of a suppressor, & able to mount some sort of optic on it, I still planning to keep some sort of peep sight on mine though.
The most accurate air pistol I have ever owned was a Benjamin pumper which I ordered from Herters (remember them?) around 1962. It was rated at 500 fps but was in actuality no where near that.
I could see the .22 pellets flying through the air. It made up for it by being extremely accurate. I worked one Christmas vacation at an orange packing house in Polk county, Florida.
When we would take breaks I would set up a penny 25 yard down on the concrete and bet a quarter I could hit it. I almost never missed. I did cheat just a bit by purposely aiming low so that if I shot low it would bounce up and still knock the penny over. No one ever noticed that I had hit low just that the penny went spinning.