Read about an interesting multi-clipboard app yesterday. Visited the developers site and found that it was only available via MAS.
They obviously already have a website. I suppose they could have an agreement that limits their bandwidth
and server space such that they can't provide direct downloads
I suspect it has more to do with Apple's "capabilities." We already know that Apple demands 30% regardless and other benefits (for themselves). It may seem easier to simply let Apple have it's way than to "irritate the beast." That, of course, is the developers choice. But it is creating a disincentive for creative ideas to come from the source of so many innovative, small, specialized people.
While the app in question was only $5, that is more than I am willing to pay for an app without any info except what is supplied by a web site with no user inputs. The "trial" use concept is the foundation that starts a process of trust-building that becomes a collection of loyal users/customers. Those loyal users usually provide new feature requests that end up creating an even better app!
I'm willing to bet that large corporate developed apps (more descriptively called monolithic suites!) have fewer satisfied users, as a percentage of purchasers, than most small developers. Like Microsoft, many of those corporations simply buy ou/up competition instead of real innovation and creative development. Of course, large and complex suites require more specialized and concentrated work by several programmers, so the development price and selling price can be extremely high. There needs to be a way for judging the usefulness of an app prior to paying for it, in my opinion. That may come with time as more people offer opinions, but opinions often don't cover the way others might use (or not be able to use!) an app.