If you create a product then there is an external cost borne by the users who need to use it. And then if you replace that product with some other product, those users need to retrain.
It's really easy to create a new product, but it is a commitment for someone else to adopt it. And just because the cost is externalised, doesn't mean it doesn't exist.
Maybe there is value for managers (who got promotions) and programmers (who got promotions and learned something), but for Google there is no value at all - it losts its users.
I remember everyone using gmail chat.. that they "remade" (killed) like two times.
Everyone just moved on.
Also I dont understand why investors arent unhappy with that. Google can still earn hundreds of millions on chat. Those wont be billions, but it is still money. And "hudred million here, hundred million there" start to add up.
There can be a lot of value in rebuilding the same things from the ground up. There'll always be differences and novel things that people earlier hadn't seen. Of course it's costly and disruptive because you kill a lot of stuff, but especially in software building new things is relatively fast.
People will always complain about companies that kill a lot of products or software but at the end of the day they get more chances to build things from the ground up.