England is a major shirt in Europe. Positions like midfield have men like Gerrard. The CB position is very expensive too, ask Carra, a man who'd be a Spanish international with no doubt had he had a Spanish passport.
But at the time Pennan's position in England was covered by Shawn Wright Phillips, IIRC, and Pennant playing well, many of us wondered why SWP had a starting eleven position while Pennant hadn't a chance in a friendly.
It's not that Pennant has shown anything worth a major team internationaly like England, it's that at the time the position wasn't very expensive. (Just as Spanish LB nowadays is not expensive)