Writing Bourne-compliant scripts ensures maximum portability. As many here have noted, bash isn't universally available, with another possible issue being Open

Writing Bourne-compliant scripts ensures maximum portability. As many here have noted, bash isn't universally available, with another possible issue being OpenWRT devices. Stock/base images tend to use a Bourne-compatible shell, not full Bash. Though the latter's installable through opkg, for sufficiently small devices (typical of consumer kit), you simply won't have the space to install them. There's also the slight PITA that Apple's OSX ships with a very old, pre-GPLv2 Bash, out of licensing concerns. (Apple is phenomenally averse to GPL-based code, much as some *BSDs are, such as OpenBSD.) And if you're dealing with legacy systems (which tend to be extraordinarily and stubbornly persistently legacy), you'll often find that either bash isn't present or is quite dated. I freely confess that I tend to write fairly recent-feature bash scripts myself by default, and appreciate many of the newer features. But if and when I am writing portable code, I'll go back to Bourne-compatibility. But when writing system level code, an appreciation for standards and the very long tail of legacy standards and the limitations they impose is in fact a large component of professional maturity.