The current bitcoin is too high to include in the campaigns instead there are many campaigns that will pay in $. I think the next $ will be the main tool used to pay for the campaigns.
The signature campaigns are not paying in USD, they are still paying in bitcoins and the only thing different now is because of the high increase within a very short period of time, they prefer to rather state the payment in USD and pay the participants the amount in bitcoin as at the payment period. It is crazy knowing that you will have to be changing the payment every now and then so as to blend with the current price as a manager.
As long as you have all the capacity to do everything this days and you are not lazy, campaigns would always seem to be the best option anyway. Ike they always say, what is the point settling for less, when you can settle for more, and the more you do with some little bit of effort, the more you get in return and the good thing is that signature campaign does not require a lot, just the usual learning, contributing and getting incentives for it.