[SoftTalker]

Many people enjoy competition and find it motivating. This is why sports are so popular, and why many organized activities tend to become competitive. Not everyone enjoys it of course, but the people motivated enough to organize large science fairs are probably highly motivated in general and that tends to corelate with competitiveness.

Not to mention that any large event takes funding. It may not be "for profit" and even if most or all the needed resources are donated there will be people competing for those donations.