I'm not sure I follow you, then. Is the MAS hard to use?
You're missing the point. Before the MAS, developers simply downloaded beta's weekly or biweekly, burned them to a DVD and had to perform a clean install with each update, over the course of 1 ½ - 2 years. That changed with 10.7 and the MAS. OS X development moved to an iOS system; $99/year from $499+, and OS X 10.x development switched to an annual release rate with ~4-5 DP releases.
Before 10.7, developers would torrent OS X beta's for non-developers on sites such as "Demonoid" (which is now down). Previous OS X development consisted of many more beta's, thus plenty were torrented and downloaded, making it much more difficult for Apple to regulate. DP's require updates through the MAS, which regulates what systems and user ID's are installing the OS whereas before anyone could burn a beta then GM onto a DVD for an OS X install (additionally OS X updates were ~$129, example 10.6).
Currently, one needs access to either the original DP (some have indicated the latest DP4 can be installed cleanly on a USB drive), then log into the MAS for DP updates. Once installed, the system will recognize the DP and will update, however some have experienced Apple cutting off access as one must be signed into their account via MAS or Xcode 5, verify development, then under "App Store" system preferences may install DP updates. In the end, Apple has tighter regulation of OS X DP usage through MAS and Xcode 5 tracking (numbers wise, doubtful they are tracing IP's), and control updates through the MAS instead of simply allowing developers to download each beta directly from their ADC account, and as the installer deletes itself after installation one must copy it somewhere else before rebooting the install in order to keep a copy. The InstallESD.dmg is no longer a simple process to restore to a USB drive for installation. 10.9 introduced a more "complex" method.
All in all, people will find a way in obtaining an OS X DP, however Apple has made it more difficult in comparison to 10.6 and earlier development. Lowering the developer price to the same as iOS ($99) has enticed more into purchasing an OS X membership account, [in theory] leading more to develop and sell app's at a 30% take for Apple. It's a win/win for Apple.
Is that enough of an explanation?
