Why Moogle's dailies random?

I knew I can do max 12 dailies.

I had "friendly" Moogle. I could be 9 dailies.
But, Only I got 3 or 6.


Why I can't be same Ixali's dailies all 12?

Moogles were always different in that respect. You get all quests for all reputation ranks from the same Moogle and he gives you 3 quests at the highest rank available.
Other beast tribes (not just Ixali) have multiple quest givers based on reputation rank. Each trainer gives 3 quests. Thus, as you got higher in reputation, you could do more than 3 quests for that tribe.

Actually, the trend noted is the difference between Beast Tribes in HW and in ARR. ARR's beast tribes had one quest giver per faction level, like the ixali (though they had an additional guy as I HW beast tribes all only have e one quest giver, who gives the highest level quests your faction level warrants.