Part of the problem is that they want to change the backends too. Hangouts had a lot of problems. Allo is their way of trying to create a clean slate and break away from the legacy of Hangouts. They can still keep Hangouts for some things, but they want to focus on a product that will get picked up by your average mobile user. People these days like using phone numbers for identification and a lot of users don't ever use a desktop. They're building for that user first. We'll see if it ever becomes a chat product the rest of us want to use.

For example of Hangouts issues, the SMS integration had all sorts of weird cases going on and wasn't reliable. I ended up having to turn it off to get texts for short-message texts from Google itself. I did some digging and since those came through a different channel somehow they were getting dropped by one of the systems and weren't getting flagged as needing to be delivered to me.

My wife also had three account entities for the same name in the Google system and sometimes her reply would get sent to a new chat. So about once a week my history with her would start fresh.

However, I agree that hangouts has been my preferred chat application for a long time and I'm disappointed how hard it is to get into the siloed worlds that a lot of chat apps have these days.