Why the AQ has no tags functionality?

Tagging is a planned feature and will be developed in upcoming releases. For now only categorization is available.

What is planning date?

At this point it is hard to tell the target date as the design is yet to complete. May be another two months would take for this to go live.

Its great idea to add Tags functionality. Keep going Maverick! Askbot for example have tags on the right side and above every question and I believe that's correct. I'm ready to help if you need somebody to test it.