Well think of the iMessage example for a second, other phone manufactures wanted to extend upon SMS with RCS to enable cross-platform read-receipts, better image quality on messages, and more... and you can use RCS between various android phones, but apple has not yet adopted RCS. Then because of the pre-existing market share of iPhones being so high, if you want read-receipts, high quality image messages, and more you with most of your contacts will either have to convince all of your friends and loved ones to use a third party app or cave and get an iPhone.
The features don't have to be revolutionary, they just have to find ways to flex their market share with their features. And their market share is almost destine to be huge if they put any meaningful effort or money behind it.