why do आप think princess आड़ू, पीच is the main princess?

Because she is pretty and girly and better than daisy

because निनटेंडो made her before गुलबहार, डेज़ी या rosalina and plus she the princess of the मशरूम kingdom :)

because she has mario who rescues her about each day.

Because Shigeru Miyamoto created Princess आड़ू, पीच to be a part of the main cast.

गुलबहार, डेज़ी doesn't get the same luxury because Super Mario Land was made without Miyamoto's knowledge. (Or so I was told.)