Why is it so small? I think it's a missed opportunity, it would have been great if it was much bigger, I mean it could have been used as a real foosball table, that would have been really cool.

No idea, but as you say, a missed opportunity I think the size they've released the set at is unplayable and it's a shame because I think it was potentially one of the best sets/ideas in terms of playability, it reminded me of the line of board games they released a few years ago, imagine if they had made them tiny....

Here is an article about it: https://brick.is/blog/post/111/lego-reveals-they-came-close-to-cancelling-21337-table-football-set-due-to-problematic-model-scale Basically, they tried several scales and while playing with the game, but the set just got ruined (broken).