Pieces of software basically never exist in a vacuum; they're always connected to other pieces of software and hardware (compilers, processors, graphics cards, phones, OSs, libraries, web services, ...). Other pieces of software and hardware always change, and if there's no one home improving this particular piece of software, it will invariably lose pieces of functionality, one by one, as they change to be incompatible with how they were before or disappear entirely because they lost to a competitor or turned out to be a bad idea.
Users know this instinctively, which is why a website that never changes loses users quickly.
Presumably the loaf of bread you bought did everything that it was supposed to when you bought it (and without bugs, or else hopefully you'd throw it away).
Software is almost never bug-free when released, and increasingly isn't feature-complete. I don't think it's crazy to be wary of using software which isn't being actively developed. It will certainly depend on what it does, and whether or not what it doesn't do (or what bugs it has) are livable.
Yeah - that is annoying. I mean my Toaster keeps being upgraded to newer versions of tOaSt, and I require the bread to remain compatible...
...there is something different about software, evidently. I want something I use to still work if Android gets updated to version x, and a dormant app doesn't normally promote confidence that this will happen.
I see your point, but — as already more eloquently explained by ecuzzillo and monastic — dormancy does eventually lead to worthlessness.
Already people are experiencing issues with features not working properly [1], and relatively simple (but non-vital) updates to add to functionality are not being made [2].
[1] I don't get RSS updates reliably any more, essentially making the app worthless to me, considering that was the main reason I bought it.
[2] E.g. the Twitter button opens m.twitter.com, not the official Twitter app. Same goes for Google Reader.
