Two good reasons. No recoil, and it cost me $.15 to shoot a PRB.
Three reasons..........it's fun.
In just got back from the range. I took 15 shots with Thor bullets and BH 209. Lets see how that works out.
Thor bullets.........$1.46 ea x 15 = $21.90
BH 209...............$.50 ea x 15 = $ 7.50
Primer.................$.05 x 15 = $.75
Total $30.15
A PRB would cost me $2.25 for the same amount of shooting, and my shoulder wouldn't be sore.