Although in numbers, techies and entrepreneurs are a minor customer of Apple, they have disproportionate influence and are trend setters.
I remember back in 2001, there was a lot of chatter among techies about OSX. It was all about how it came with a BSD licensed core, good terminal, a standard Unix environment, Perl out of the box, etc.
It was a fresh alternative to Windows which was a lot more open than iOS of today but still pushed software development in non standard and monopolistic directions compared to the Unix based OSX.
Thus began the rise of OSX. It was a credible technical platform and at the same time it would spawn some killer consumer features, a nice and fast simplified desktop environment and well integrated innovative consumer accessories such as the iPod. Sure Apple pretty much always limited their OS to their own hardware, but it didn't matter to techies as long as they played well with others by staying mostly compatible with Unix standards. Entrepreneurs were also free to sell software for it directly to their customers. You could buy a subscription on the devices without giving 30% of the revenues to Apple.
I tried to run a Perl script on my mac the other day and a perl module wouldn't compile because of some error with PowerPC compiler flags. PowerPC! Clearly Perl on OSX has not been maintained for a while.
I'm currently writing a subscription web service along with apps and the 30% cut to Apple is a dilemma for management.
Amazon doesn't let just anyone run apps on their Kindle devices either. However Amazon devices are meant to be pure consumption devices mostly for Amazon products whereas Apple wants iOS to be the main computing platform of the 'post PC era'. Pure consumption devices have a much more limited market than computing platforms. When Apple locks up their platform they are limiting themselves to this much smaller market.
No developer wants their computing platform to be locked down, non standard and encumbered by huge revenue levies.
The software development and entrepreneurial world needed a credible alternative thus came Android. None of them wanted another closed, non standard, fee encumbered platform thus failed, Palm, BB and Windows Phone and eventually Apple.