Why? Because we can.
A playful answer, but more often true than not. If something works, why not keep doing it? Marketing and sales are areas where this attitude is so entrenched that some people never question it. "Always be closing", "sell sell sell". Why are we pushing this grandmother to buy an android device she'll never use? Because we can.
We put all the responsibility in the hands of the recipient, the buyer, or the clicker of ads. Often rightfully so, in my opinion. As good balance to douchy sales tactics is that if people simply don't buy, the salesmen will quickly stop and try something else instead. Other fields are not so clear cut though.
As designer we believe it is our mission to delight users. To make the product easier to use, more entertaining, and always more sticky. Last week my favorite gamification researcher, Sebastian Deterding, posted a keynote where he questioned this idea; Why is it our job to make things more sticky? I found myself agreeing wholeheartedly. No matter if work with web or apps, you are providing either tools or entertainment. There really is nothing else. Entertainment should of course be entertaining, and I wont rant about game design in this post. But should tools be fun? Should they be sticky?
Steve Jobs once described the computer as a "bicycle for the mind". A tool to reach farther and faster than a human could without it. But are computers living up to this promise? I would argue no, and it's because of us. As designers, we've perverted the idea of tools. Creating hammers people really like to use instead of ones that gets the job done. We're not looking for the best way to solve a problem any more, we're debating how to make our users engage more with the product. Again something which is fine, if it's entertainment. But if it's a tool, this is a douchy sales tactic.
I think we need to stop talking about delighting our users and get back to trying to build the best tools for the purpose. No matter how good we dazzle our clients, eventually the sales pitch will end and the users are left holding chocolate hammers.