Due to a couple of reasons:
If someone wants to write a patch for it, I will seriously consider adding it. I believe that safely adding 2FA would be very time-consuming, so I'm not willing to do it myself or direct Slickage to do it.
2FA is apparently fairly difficult to integrate into SMF (the current forum software).
This is enough explanation for the reason why there is no 2FA now, and a sound reason also to hope on the future introduction of 2FA when the new program is launched. And this dates back to 2014!! Be patient and don't be clicking the phishing links that could compromise your account.