Both arguments are not sound though, and as a result demonstrably irrelevant. The title of the thread and the argument in the GP is based on features present in ZSH but not Bash and the benefits there of.
The OP's first argument is: for all operating systems Bash exists. Which, while also untrue is and unrelated to whether ZSH has features or improvements that Bash does not. OP's second argument is: all ZSH users also program in D...., which I won't even bother with.
For what it is worth, I use both Bash and ZSH. Their usage and knowledge there of is not mutually exclusive. The only issue I've encountered with using ZSH is that most build scripts expect to be ran from Bash and will run into issues when that is not the case sometimes, so I open Bash before running the command if I happen to be in ZSH at the time.
If I based my tool choices on popularity instead of their appropriateness for the problem domain my work flow would look much different as well.
