The lack of elaboration to the question shows that there wasn't much thought put into this idea IMO. While a majority of Americans use iPhones, there is still a significant portion of Android users. It's unfortunate that an interoperable solution was not promoted, but I assume this suggestion attempts catering to the majority and puts little thought into what we are all concerned with -- interoperability and being able to target everybody, not just ~60% of the U.S. population (if you want to believe statcounter's numbers).