Sketch by Bohemian Coding is one of the most famous vector-based wireframing apps available on Mac App Store. According to the company blog post the reason behind leaving Mac App Store is bad customer service. According to the Sketch Blog,
There are a number of reasons for Sketch leaving the Mac App Store—many of which in isolation wouldn’t cause us huge concern. However as with all gripes, when compounded they make it hard to justify staying: App Review continues to take at least a week, there are technical limitations imposed by the Mac App Store guidelines (sandboxing and so on) that limit some of the features we want to bring to Sketch, and upgrade pricing remains unavailable.
Compared to the iOS App Store, Mac App Store is smaller but still it takes almost a week for the app to get reviewed and cleared by Apple. This often makes upgrading apps a big hassle. Besides, Bohemian Coding was also facing problem charging for the upgrades.
Although Bohemian Coding claims that it is the lengthy decision-making process that has forced the company to remove the Sketch app from the Mac App Store the real reason behind the decision, many industry experts claim, is the prospect of making more money. Which of course isn’t wrong.
When Apple developers sell their apps through Mac App Store, they have to split 30% of the sales revenue with Apple. Since Sketch already has a big market and there is an ecosystem of tools and applications that is being developed around the app itself, maybe it doesn’t make sense to pay Apple for making sales when people can directly buy the app from the company’s website. The blog linked above also provides instructions for Mac App Store users who have already purchased the app and would like to migrate to the directly licensed version.