Is this basically why things like Inbox, and the endless attempts at messaging, all come out as seperate products rather than enhancements to existing products, because that way you get to say you launched something new?
The thing with Big Ideas, is that they're often iterations of existing ideas, but just different enough that you can make a case for a fresh start. (And who doesn't want a greenfield project) Plus, the cost of experimentation is far less while you're not supporting a massive userbase.
WhatsApp had the advantage of growing slowly and segmenting their users with time to experiment and tweak things. The Google chat apps came out at once, and it’s possible there were so many because they tried to come up with a working segmentation for all addressable users from day one instead of growing organically and grabbing each segment one at a time.