I respect third party marketplaces and what they bring to our ecosystem, I use them every day! This proposal doesn't aim to punish them, it aims to better align incentives.
Currently, there are marketplaces that offer cashback as a service who are taking market share from platforms that actually provide development value to our ecosystem. Part of this proposal is taking away some of that power to make sure market share actually scales with utility.
As for the DEC going to the DAO, I like to think of it as our community fund. We will be needing it once SPS emissions end but before then, the community has the power to do anything we want with it, including simply burning it all! I personally believe providing a consistent and long term income stream for the DAO while taking DECs out of the current circulating supply is incredibly important and this should single-handedly outweigh the all the downsides I listed above.
deleted previous response as authored from wrong account
when the sps emissions end, what exactly does it get us if the dao then has dec? if we really want dec at that time, splinterlands could just print dec again this is not a limited token.....