Hunting scopes are for full bore, few are parallaxed to air rifle ranges. Have to go down to x4 to work at very close farmyard ranges. x8 or x10 really require side parallax and no one goes there as may as well go variable. As it is air rifle has got more sophisticated and many demanding even higher power for parallax range finding.
Scope manufacturers are only recently taking note of what people actually want. The American market leads.