Open datasets are hard to come by. It's potentially easier to find problems to solve by looking at the available datasets than seeking datasets for the problems you wish to solve.
When you want to create a new website do you start by looking at a bunch of clip art and images? Browsing through datasets such as the ones listed in this thread leaves me overwhelmed. I've never had any difficulty finding open datasets. If there is a dataset I need that doesn't exist or costs money, I find a way to create it from scratch.
Datasets aren't always quested for. Sometimes you want a specific dataset to solve a specific problem, and sometimes you'll take any dataset just to see what you can learn, or to make interesting infographics. Lists like this help the latter situation.
