when i bought my 2005 innova, i was all praises, including the cold and strong aircon. i had it serviced always in the casa, because of the warranty, and because tamad ako.
i found out after 3 years (wana warranty) that i had no aircon filter! i found out because i was having it serviced outside, and it was the banawe guy who informed me that i had no aircon filter (after all these 3+ years?!!). well, we looked around for a discarded filter in the shop, found a dirty one, cleaned it up and installed it, all free of charge. ok na saken used, mahal ang bago, e. hanggang today, 5 years later, it's still with me. i just wash it periodically.
when i bought my second innova in 2012, same casa, first thing i noticed was the weaker (compared to my first innova) airflow from the aircon vent. and true enough, when i checked, the aircon filter was there.
i believe that all them toyota cars come out of the factory, with aircon filter installed.

but is it possible that, because the aircon will work anyway and because it takes some hand acrobatics to check, almost no one checks their aircon filter when they buy the car new..?
that the casaboys know this, and target the new filters themselves... no one checks, 'di ba? easy money..

i had my 1997 sentra for 14 years.. i still do not know where the aircon filter is located, if it has one even.. and i consider myself more knowledgeable than the average owner..