GazWhat is this nonsense?
If I want to improve, I don't pick someone who is miles ahead of me to practice with.You can't improve if you get flawlessly 5-0'd by a far, far more experienced and skilled team.If it is a open/mid tournament, alright.But you can't ask beginners to play with semi-pros or veterans.
You don't see people going to the gym like "Yesterday I benchpressed 50 KG, today I will go for 80 KG!"
The whole point is that if a lot if people sign up, it is much more likely for you to lose to teams roughly around your level (or at least not leagues above you) besides maybe once (if it's double elim)
Cups/tournaments are definitely a good way to improve; matches always put more pressure, even if you're not going to win the whole thing.