Why isn't the
tabular environment enabled in MathJax? Is there any work-around for making tables?
tabular is not a Math environment? Why should it be part of MathJax?
(BTW, "feature requests" for MathJax should be filed with the MathJax developers, not here. And if you do so, you'll be quickly pointed to the fact that they were asked before about it, and decided that it is rather pointless to implement a table environment in MathJax when HTML does it just as well.)
If you mean a feature request for MarkDown, please file it at Meta.SO. And of course, if you filed it, it would be closed as duplicate because someone else asked already. There you will also find a possible work around by abusing the code environment.