Christ, your patronizing attitude toward software developers makes me sick.
What do you think we are, children?
I write programs which are dependent on third-party software all the time.
More specifically, I have never written a program that doesn't. There is
nothing special about a programmer choosing systemd as a dependency. It
happens because the programmer wants to use systemd, not because of some kind
of mass conspiracy to force him to use it.
But hey, if you want to talk about non-portable dependencies, how about X?
You know, the window system most commonly used for the last ~30 years.
Seriously, it's exactly the same deal. You'll find several programs in
Trisquel's repo dependent on X,[1] and in particular every screencasting
program for GNU/Linux is dependent on X. From my understanding, Mir and
Wayland either have implemented or are implementing X-compatible interfaces
specifically because of this. You know, kind of like when the BSDs make
systemd-compatible interfaces they can use.
Neither X nor systemd are grand conspiracies. Please give us programmers some
credit, rather than assuming we're nothing but sheep being herded by the evil
systemd superiority conspiracy.
[1] A short list of some examples: recordmydesktop, xbill, xjump, xgalaga,
xpuzzles, xsol, xscavenger. Lots of other packages with names that begin with
"X" also fit the bill.