Why 3 days per move time control?

For daily chess, it does not make sense that it is 3 days per move, because players can play quickly in the opening, but might need to save time for a complicated position. Why don't they use a standard correspondence time control, like 30 days for 10 moves, or something like that?

For players who have experience playing the real correspondence time control, what is your experience of that vs. the 3-day per move games here on chess.com?

No, but I mean why is it "time per move" and not "time per moves"? Doesn't it make a lot more sense to be able to allocate more time to the critical positions instead of equal amount of time for all moves?

Especially if someone is playing many games at the same time, it would be even more valuable to be able to allocate time.  

As a nube without a bunch of openings in my mental database, I love 3 days per move.  One day to explore the possible, one to settle on  "best" and one to change my mind.  Rationing days would just give me one more non-position thing to think about.

.