Call code behind function using anchor tag

I have always been banging my head for this:
Why <a runat="server" onclick="CodeBehindFunction()"> does not work (in simple html without databound controls) even if we make it to run at server?
(I know we can always replace such anchor requirement with asp:LinkButton as it ultimately get rendered as anchor in html.)
I just need a justification to the above question/issue!!!
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