same problems over here at BCAC,
the reason is simply because of the legal paperwork that goes on between their lawyer, and insurance company.
The fact that it is a paintball field, they need to make sure everyone is wearing a paintball approved goggle. Its not important if it can withstand a bomb, the fact is simple, Paintball only.
that said, there are some ballistic goggles that are "paintball rated" ESS for example.
It sucks royaly, but paintball is their bread and butter, and they need to keep everything based around that, Paintball.