As pointed out by others, your question did receive an answer from us. See below.
Why do you pay signature spam bots to represent your brand?
For starters, calling them "spam bots" is probably not justifiable. If you can show me any spam bots, I'd be delighted to remove them for low quality content.
If you want an honest answer as to why it's happening, it's one of many tactics we are using to build brand awareness since we are a fairly new website. Additionally, engaging with the community is helpful as BitcoinTalk has been a very useful tool in identifying things that they would like to see as our project develops. The signature campaign accelerates this aspect and pays some indirect dividends to us through this and other ways.