I am sure irfan_pak10 is a Muslim and Muslims usually take gambling as a sin, I think that's the reason for his non-interest in gambling campaign.
I really don't know anything about Muslims, why can't they be involved in gambling? This is not gambling, it is advertising, advertising work why not allowed 
I am quite curious about it 
As a charity campaign, I think it should be applauded for participants to carry this signature for free
And by the way, if ever that you are still seeking an answer to your question, here is the answer.
I am sure irfan_pak10 is a Muslim and Muslims usually take gambling as a sin, I think that's the reason for his non-interest in gambling campaign.