I feel like using Bash is a double-edged sword. Yes, it's available on every modern unix-like (notably absent from the base system in the *BSDs), but the language (being an sh descendant) is honestly horrible for anything more complex than 200-300 lines of plugging one command into another. Ticket isn't even pure Bash; it embeds several inline, 100+-line AWK scripts, and a giant jq query (an external tool!). All of which is horrible for syntax highlighting, mind you.

These days Python is almost as universally available, and I've seen few systems ship without Perl. Both provide excellent backward compatibility; I have many scripts that still run unchanged on Python 3.6 (2016).