Because it is ruddy difficult. There aren't many teams who even try to press as far up the pitch as Spain did last night. If it goes wrong you leave big holes to be exploited, or even worse, acres of space for forwards to run into behind the back four.Why would we get slaughtered? If the whole team presses then it could work, if only a few players press then it is a waste of time. All pressing requires is a high level of athleticism and organisation.