This topic has been covered quite extensively over the years because the usage of this feature is often misunderstood across all Stack Exchange communities and sometimes used as workaround when a contributor feels that they generally shouldn't post anything at all (but they are overly compelled to help the OP).
In no particular order, here are some references:
If you don't have time to read all of that, my personal opinion is that you should only tick the wiki box on your post if you know that you do not possess all of the necessary wisdom to provide a complete answer. This signals that you are actively encouraging edits from other community members to make your answer whole. Beyond that, I find no compelling reason to use it. If you never post a Wiki Answer -- that in no way reflects that you are under-utilising this community's features.
You can find all community wiki posts in a given Stack Exchange community by entering
wiki:1 into the community's search box. On JSE, https://joomla.stackexchange.com/search?q=wiki%3A1 is currently showing just 11 Answer Wikis.
This is an opportunity to explain that Tag Wikis are different from Answer Wikis. JSE would really benefit from members of our community sharpening up our tag descriptions. There are many tags that have no descriptions or usage instructions. It is a bit of an artform to make great suggested tag edits, but there are rep rewards in doing good work. Visit a few of Stack Overflow's tags to see examples of high quality tag edits then blend that with your Joomla knowledge and help us with our tags!