This is a free service. It is used hundreds of times a day. The percentage is changed based on usage. If the bot is not used as often, the percentage goes up.
Keep in mind, as the bot SP grows, the percentage will have more and more meaning.
The purpose of @OriginalWorks is not to just give away free money, but to curate original material. The upvote is a bonus. For now it is worth a fraction of a cent, but in due time it will be worth more :)
The best original material gets resteemed, and sometimes users get prizes!
I totally agree, thanks for your reply. My question and your answer probably will clarify this point to others