I used to reason exactly like this, but then in last few months occurrences of this rare cases of bugs in OS, environment or even hardware started to be little

I used to reason exactly like this, but then in last few months occurrences of this rare cases of bugs in OS, environment or even hardware started to be little to often. Although I might be biased by spending inordinate amounts of time on these bugs (like one day each). Various X11 related bugs (well, when X server crashes, you can be pretty sure that it is not bug in _your_ code), Windows driver bugs, Windows hotfixes fixing one bug and exacerbating impact of another bug from "minor annoyance" to "does not work", RTC chip with errata longer than datasheet, weird firmware<->kernel interactions, generally failing hardware and so on.