The market is a battleground for every little space for the promotion of the projects. Everyone wants their own space under the sun so offering something is more efficient than limiting someone or something. You can choose anything you want though. There are so many interesting projects out there with good bonuses where you can participate.
I agree that the more is the merrier and this is one of their marketing strategy, just join in the club and leave those spammers out there. Just leave it on the manager to handle everything besides you are just only participating and it is their project, i mean we are just doing what they want us to do in order to gain something from them.