What do you mean by iPhone button? Do you mean sets that have a single answer/end/mute/pause button on them? Those headphones work with all kinds of products, not just Apple, and AFAIK, the design predates the iPhone/iPod's use of that feature.

The iPhone-specific ones seem to be the ones with three buttons on them, two of them being for volume control.

As to why manufacturers make such headphones it's because a market exists for them, whereas, a market doesn't exist for other handset makers because none of them have likely standardized on a set of controls. The "problem" is easy to fix. The head/earphones are already widely available from countless manufacturers, time for these misc. handset manufacturers to update their specs and software to support them.

As far as products that fit well into the ear, there are a lot to choose from. I like my Etymotics, which I picked up this past december. Other people swear by Shure and Ultimate Ears.

For control, you could always hack apart your current earphones and then also hack apart a control adapter specific to the iPhone/iPod to see if you might make any mods. I've come across some discussion of using adapters with different phones while researching headphones last year, but not specifically making any mods. It's possible someone has already done this.