Inkidu said:
They ask you to turn you cell phones off for a reason in most theaters. If you're too stupid or too unwilling I don't want to know you, and if you're too busy, why are you watching a movie?
Or, just maybe, the person has a loved one with a condition, and wants to make sure they are able to be reached at any time, which means leaving the cell phone ON. But hey, its not your family so what would you care, they're just an unwilling idiot who should be chained to their house.
I leave my cell phone on when I enter a movie theater in case something happens with a sibling of mine, and I need to be reached.
I also sit in the far back usually, with my phone on silent, so if I do ever end up having to text it won't bother others.