Why don't I see a ceiling icon for all airports on the Maps page?

A ceiling icon is only displayed when at least one cloud layer is reported as broken (bkn) or overcast (ovc). A ceiling icon will not be displayed when cloud layers are reported as scattered (sct), few (few), or clear (clr). 

Also, a vertical visibility extending into an obscuration counts as a ceiling (ie: VV003) and causes a ceiling icon to be displayed on the map.

Image 1.  Ceiling icon is displayed due to a broken (bkn) cloud layer at 25,000 feet.

 

Image 2.  Ceiling icon is not displayed due to all cloud layers being listed as few.