There's probably several reasons for this, but one of them is that it's hard for the yobbos to get into club stadiums. Since Hillsborough there's been a huge clampdown, especially at the top clubs like United and Liverpool. Lots of miscreants are permanently banned, and you normally have to register with the club to apply for and buy tickets.
I imagine for England games there's nowhere near that level of vetting, or it's easier to bypass of you know how. Then there's the fact a lot of hardcore England followers are fans of lower or non-league clubs, where it's still very much a place for young lads to get mashed every weekend.