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.
The reaction has rekindled the debate about the viability of the Mac App Store (MAS) for developers—at least for indie Mac developers and those who make more niche, more productivity and utility apps.
Much of the debate has focused on the reasons stated in the Sketch post, on the perennials—trial periods, upgrade pricing, direct customer relationships, freedom from sandboxing, disintermediation of review, etc. All mechanisms and realities from a time before mobile shattered the expectations associated with traditional software businesses.
They're easy to point to, and have nostalgia on their side, but it's tough to say what if any substantive difference they'd make in the post-"pop app" world. It's one of the many reasons why presenting perceived solutions to a problem is never as productive as stating problems and leaving them open to potentially novel solutions. It's the "faster horses" trap.
We live in a world now where apps are cheaper, more plentiful, and more available than ever. Companies like Apple, Google, and Microsoft give away—even pre-install—highly crafted software subsidized by their hardware, services, or enterprise businesses. Venture capital funds development disassociated from profitability. App Stores and the modern internet allow for easier and far more accessible distribution than ever.
Customers, especially the vast mainstream majority, spends more time on the web and now phones than they do desktop software and phones, and that has dramatically changed expectations. We've become less and less inclined to pay for things, including music, videos, news, and, of course apps. Not just up-front but at all.
We're also moving towards a world where what it means to be an app is changing. Just like web services have become decoupled from web sites, app features have become decoupled from app binaries. They already extend into widgets and share sheets, project across watches, TV boxes, and dashboards, and handoff between platforms. That's after less than a decade of App Stores. What will they be in a another few years? How is that kind of software/service made discoverable, available, and sustainable?
There are likely no easy answers, especially when you start to consider the repercussions. But solving hard problems is Apple's job. They wield the greatest power in the App Store so they bear the greatest responsibility.
No app is entitled to exist and there are certainly no guarantees for success. Yet the App Stores have always felt at least partially predicated on giving apps a better shot, especially indies. They made app delivery accessible to everyone.
That said, it's possible that Apple is fine with Sketch, BBEdit, and Coda leaving the Mac App Store and many apps never entering it at all. Apple created Gatekeeper, after all, to allow for trusted app delivery outside the Mac App Store. It's part of what makes the Mac App Store distinct from the iOS App Store. Apple might well think the MAS is best suited for pop apps, and pro or niche apps can and should exist outside it.
It's also possible Apple simply doesn't see the MAS as a priority. Even though they're distinct, the Mac App Store shares resources and attention with the iOS App Store. Since the Mac App Store is a much smaller market and earns a tiny fraction of the revenue, almost all those resources and attention go to the iOS App Store. There is no single, company-wide executive running and championing the entirety of App Store as a product, much less Mac App Store.
As a result, the Mac App Store trails far behind the iOS App Store in terms of features for developers like TestFlight and analytics, as well as for customers, like app-gifting, bundles, per-category features, video previews, and more. (That the Mac App Store.app hasn't seen any major updates since launch should also disabuse anyone of the notion unbundling from iTunes.app, in and of itself, accomplishes anything.)
To get the Mac App Store to parity with the iOS App Store would likely require the establishment of a high level position within Apple directly responsible for Mac App Store success, with a distinct team dedicated to delivering it. And that would likely require champions within the Mac product team and a major release it can piggy-back on. Something that makes it a priority at the executive level. Not because it's market size or revenue demands it, but because it increases the overall value of the Mac and it's a point of pride.
(The shadow cast over the Mac App Store by iOS isn't dissimilar to the shadow cast over the iPad by the iPhone, so looking at how the iPad Pro drove features in iOS 9 wouldn't be the worst parallel to draw.)
That team could then figure out what, if any, features need to be added to the Mac App Store to make it a first class experience. Not just because it would be better for developers, but for customers and for Apple.
And if some apps still don't suit the MAS, if its still more for pop apps than niche apps, than it can be due to activity, not inactivity, which is infinitely more palatable for everyone.