yeah, public API...
well, who is interested in a public API?
developers?
as a matter of fact there are usually a lot of apps for a single organisation, many of which created by 3rd parties, either with commercial intend or "freely" (or as adware)
either way, there has to be some API available.
but at the end of the day, the vast majority of users just want an app which not only shows them information but also allows them to interact, like planning a trip or even booking it...
and there, the number of devices running on an OS obviously matters.
if i would develop (& maintain) myself all the apps i found in a few hrs for Android, i could be busy full time.
only, the number of ppl interested in using it, leave alone paying for it would be so small, it simply never would allow for a living
alas

unbelievable that from the most used (& sold) platform three years ago, NOKIA went to oblivion because of one m0##0n
flop deserves to be cut in pieces and fed to the porks