When opening JMeter 3.2 GUI WorkBench exists always
WorkBench also can't be deleted although when saving Test Plan, WorkBench isn't saved by default.
It's also confusing for newbies that we can add logic and samplers to WorkBench which won't be executed and saved.
I almost never use WorkBench so I wanted to know why WorkBench is important in JMeter.
Why WorkBench is shown as default in JMeter and can't be deleted?
Imagine you have a wood shop. You have a WorkBench and you are building a bird house (Test Plan). Sometimes, you need to get out your saws (Test Script Recorder and Recording Controller) and other tools. You have wood (recordings) on your bench that you aren't yet sure belongs on your bird house. When you leave your wood shop, you don't care about anything that is on your WorkBench you only care about the bird house you are working on. When you come back, you want to only see the birdhouse and an empty WorkBench. So after you leave, your housekeeper puts the tools away and throws away all the scrap wood you have on your workbench.
So that's how to think of it. Primarily, it is a place to use your Test Script Recorder. If you don't use this tool, the Workbench probably doesn't make as much sense. When a system I have been testing on does an upgrade, I sometimes will open the JMeter script I have and do a new recording to my WorkBench and then compare to what I had previously recorded to see if any changes in the API calls have been made. It keeps things tidy because the last thing you want is some extra junk call in your test plan that you didn't want there. Sometimes, when I'm debugging a certain call(s), I will copy the old stuff to the work bench, just incase I muck things up in the Test Plan.
It appears that my question lead to a new enhancement of UX : Remove Workbench
Currently not developed (in status NEW).
EDIT
Workbench was removed in JMeter version 4.0!