the iphone is one of the most popular phones in japan right now. mainly because of ease of use, especially with inputting japanese. i'd say about 50% of people using smartphones are using one. the iphone does have a few limitations that irritate me and other people, this being one of them. a lot of things in japan accept these contactless payment systems, from vending machines to arcade machines to the train station. every phone has them EXCEPT the iphone. that's why people have been using cases and stickers that have the cards in them. the problem is it doesn't interface with the phone and so it doesn't give you the full functionality of other phones.
the other thing the iphone is missing for the japanese market is being able to watch 1seg broadcasts. everything has a 1seg tuner these days, whether it be phones, your car gps, or attachments that enable your psp and ds to have them. 1seg is a mobile broadcast method that allows you to watch the standard 12 channels or so. it's not going to give you the awesomeness of satellite, but at least you can watch NHK, TV tokyo, Fuji TV, TBS, etc.
TDLR: why can't my iphone work with suica