Google’s Allo chat app isn’t blowing up the app charts (not that it ever really did), and part of the reason might be that it’s limited to a single device. Google had the admirable instinct to create an app with a “mobile first” mentality, basing the app on phone numbers instead of Google accounts. That made setup easier and potentially could have helped the app spread, but it also meant that you could only use it on your phone. Not having a desktop client seriously hurt Allo’s chances amongst early adopters who, it turns out, have laptops.