Well... a similar thing happens to Facebook and even some shopping sites as well (I've been buying from Book Depository each 4 months since the end of 2013 and last month they sent me a discount coupon with a message like "we miss you, take this coupon" because I haven't bought anything since the beginning of the year). In Facebook, when you have a page, they encourage you to post there; the same thing Tapastic does.
Anyway, it's their business, and they want to keep it alive. By publishing and generating content the business earns money according to the exposition of ads and it keeps them alive so we don't need to pay to use it. Like, in Tapastic, we have an integrated community and all the support of the platform.
Anyway, sorry, I got carried away .-. Just wanted to write a previous explanation in order someone questions the utility (and kinda the ethics) of such emails.