There are some project that defines the limit of participants in their campaign, some even intentionally screen out with ranks, like "you must be at least a senior member to participate", some will intentionally give a high task to meet up with such as 20 post with 150 words and must be spread across 4 days, and many more.This is to make the token more valuable.
If there are many good projects people will have options than rushing of the very few ones always available.