because each part of the UK feels it has its own football culture
and a Great Britain side would have a ridiculously high proportion of English players
the other 3 areas simply wouldn't be represented
Can you actually think of any Scottish / Northern Irish / Welsh players that would actually get into the England squad?
track and field/ winter events are obviously not as much to the forefront of a nations sporting culture as football is, within the context of the United Kingdom - I don't think those sports have the same universal grass roots status that football has, whereby the sport permeates all levels of society regardless of class, location etc etc
Also, without really wanting to bring politics into this, there are many Scots and Northern Irish who from a cultural/ political standpoint would never want to represent 'Great Britain'
I remember a while ago that Rangers and Celtic tried to enter in the EPL saying their league is not competitive enough, I wonder how they would have felt about there being a Great Britain national team?
Different football culture isn't exactly a bad thing...it's good to have different options but yeah I really don't think the football culture of these countries are different, I feel they're very similar style; ofcourse England are of higher quality.
Anyways, Spain could be an example of different football cultures... you have Barcelona's La Masia type of footballers combined with other schools of football in Spain.
Just imagine England having Giggs and Beckham on the wings for England.. they could've have literally played 3/4th of Manchester United's treble winning midfield of Giggs, Beckham and Scholes.