No that is not the main reason on why newbies are very rare to participate in a campaign although it is posible to join a bounty even if your a newbie because in the altcoin bounty section some of the campaigns there are still acepting newbie ranks. newbies are limited because they can likely cause spamming and can also lead to greedinees because user  can always create multiple accounts in order to enroll in again and again on a single campaign. The campaign will drain dry if newbies will always accepted.