Why not plumb cold water into bottom of HW heater?

[homeby5]

Just curious. Why not run the cold water into bottom of HE heater, thereby eliminating need for dip tube?
I'm thinking of running mine into drain valve outlet and putting in a valved tee to drain when needed.
Be easy on me...I'm ignorant of this stuff and thinking out loud.
Thanks

 

[breplum]

conceptually sound