Because those who have money and time can work for change while those who have neither are working to survive. Your rich kids can take off across country to attend protests without losing jobs or using up the family's food money for gas. It's yet another reason it's important to empower everyone financially, to give them the ABILITY to work more effectively for change. You don't see protest organizations who say 'don't support us financially!'. They know they need the money to move protesters, to feed them, to give them temporary housing or tents and so on. Money feeds the ability to create other changes.