The Mac App Store is absolutely horrible (lots of bugs, slow, inconsistent, almost unusable, absurd certificate expiration issues that are completely embarrassing for a company like Apple, etc.) and Apple has completely ignored all developers who use it... but this is exactly why I always prefer buying from it. I don’t want some nobody developer harvesting my information, and selling/renting it off to some who knows who either now or some years down the line when the company folds.
Please have respect for your potential paying customers and drop these kinds of practices. Other than recovering a potentially lost license key, there is absolutely nothing I need from you, including any and all “news or updates”, after I have purchased the app. Therefore you should only really need some unique value (like the hash of an email address) for that.