Why air condition re-cycle inside fresh air from outside?

It's a matter of sealing of windows and door ...they are almost airtight

The air conditioner recycles inside air because it is already cooler than the outside air.

An air conditioner most often works just like a refrigerator.
The air within a dwelling is recirculated, for the most part. The internal hotter air is cooled and fed back inside, the heat is transferred to the environment. This makes for best efficiency.
Most homes are not tightly sealed, so leakage from outside is sufficient to replenish oxygen. If too much hotter air is taken from outside, the efficiency drops off.
Large commercial installations use more air from outside and cool it, as there is likely to be many people inside at any time, e.g. in shopping malls.