If the rates aren't attractive, they wouldn't stay until now.
Not everyone prefers switching campaigns.
Moreover, if the rates are attractive, they might have got many applications after announced about open slots but since 24 hours, there were no applicant.
(I am not here for picking up a debate on this; let Stake decide everything).
If you weren't here to debate, then you wouldn't have opened your mouth honestly. Campaigns offer what they want to offer. You can choose to apply or not apply. Really no reason for anyone to say a word about what a company offers. Your arm isn't being twisted to join.
Higher rates can attract better posters, but better posters can also be found in the lowest ranks.