My guess is that it's a few things: 1. Long form convo on mobile sucks, so instead we send memes but chat just wasn't ready for that. 2. iMessage defaulting t

My guess is that it's a few things: 1. Long form convo on mobile sucks, so instead we send memes but chat just wasn't ready for that. 2. iMessage defaulting to non SMS but proprietary, now sms has the features we want in mobile conversations like quick picture sharing, likes, memes, consistent emojis. 3. At the advent of iMessage, google had talk and could easily have transparently merged sms and xmpp in a shiny competitor that was cross platform, and worked everywhere. They failed to see any value in this, and instead have released a revolving door of halfass chat apps, half the time more than one at once, with a subset of the features of any normal chat app. 4. From there, everyone just made a platform specific chat app, because cross platform ease of use was of no value as there was no competition in that space.