It also states that it's for the purpose of promoting the creator's content on Patreon. For example, showing a thumbnail image of your video on another page as a recommendation would count as a 'derivative work.' Without this right, it would be virtually impossible to get permission from the creator for every instance in which Patreon wants to promote content in a new way. Also, it seems that the creator on Patreon would continue to benefit when Patreon earns value on the content.

Facebook, on the other hand, has numerous ways to benefit that don't proportionally benefit the creator, including from indirect revenue sources like advertising and data enrichment that don't flow back to the creator in any way. I suppose this is alright when you are just showing cat photos to your family, but it's quite different when you are basing your business on someone else's market-dominating platform with large negotiating leverage. And there are known cases where Facebook has been known to very liberally appropriate ideas from companies that are competitive with them (e.g., Snapchat).