The benefit of pulling the goaltender in hockey is not really comparable at all to doing the same thing in soccer. The games are structured differently enough that tis strategy, which constitutes fairly standard practice in hockey, would be extremely unlikely to have any real effect in soccer.
First of all, adding another attacker to a 10-man field unit is, merely going by percentages, about half as useful as adding another attacker to a 5-man field unit. Furthermore, as others have stated, the ease or difficulty of scoring in soccer is not necessarily related merely to the number of players you push into the attacking zone. Sure, having three men attacking in the box is more likely to produce a goal than have one, but there comes a point when adding more people does’t make things easier. In fact, with too many men forward it’s easily possible for attackers to get in each other’s way.
Another reason it’s difficult is that, in soccer, no matter how many men you have forward, you are still constantly vulnerable to the offside trap. And if you’re called offside, your attacking raid ends immediately. This isn’t the case in hockey, where the offside marker is a fixed line rather than a moving plane. As long as the puck crosses the blue line first, everyone who follows it into the offensive zone is onside for the rest of the play, and there’s no possibility of an offside call until the puck crosses the blue line again. In soccer, on the other hand, an offside call is virtualy always a possibility, even right down in the offensive zone.
Also, the range of possible scoring shots in hockey is such that an extra attacker can be a big help. In hockey, it really helps just to get as many men as possible around the net. Not only does this obscure the goaltender’s view, but the slightest deflection from a stick or skate can turn a shot past the goalie into the net. This type of serendipitous deflection is much less common in soccer, and simply pouring men forward is not really the answer.
Having said all that, i do remember once seeing a soccer goalkeeper up in the opposition penalty area attempting to score. It was some years ago (mid-1990s?), and Manchester United were playing a Cup tie of some sort. In the last few minutes, they got a corner or free kick, and every player on the team, including goalkeeper Peter Schmeichel, was up front trying to score. But i think Schmeichel was there not just because he was an extra player, but because, at about 6’4", he was one of the tallest men on the field, and thus had a decent chance of getting a head to the cross. In the end, Man. U. failed to score.