...or not being in a market where no one knows how to make money. The best exits are for the companies that don't need to.
TweetDeck could make barrels of money if Twitter allowed them to run adverts. (of some capacity)
Tweetdeck could run adverts just fine, Twitter just didn't want them running them in a sketchy in-stream manner, which I think is fair since their whole app just sits on top of Twitter.
And running adverts wouldn't destroy a huge portion of the userbase?