[mcpackieh]

> Why do there have to be so many different: [...]

Different shells/etc exist because people have different preferences. If all of these options didn't exist, then more people would be stuck with software that misaligned with their preferences.

> global man hours wasted

It's not effort wasted if the people who made all these things felt fulfilled in doing it; their effort was only wasted if they don't value their own work. There's no opportunity-cost to consider unless you think these people would have otherwise been devoting their manpower to some other FOSS project instead instead, which is a bad assumption. Somebody who wants to write a new shell does not necessarily have any interest in writing something else instead. Community FOSS development isn't like commercial software development, volunteer developers aren't "human resources" that get assigned to work on things that don't interest them. If for instance the fish shell didn't exist because it's technically redundant with bash, there's no reason to think that manpower would have gone to another FOSS project instead; the developers might instead have chosen to spend their time fly fishing.

If somebody's hobby was building model ships instead of unix shells and they built a model of the Titanic, would you say their manpower was wasted because thousands of other people have built similar models before? That's not really a reasonable way of criticizing hobby projects.