Not necessarily Amazon, or Google, but the third parties which use those voice assistants. They have their own applications, and servers they use so you can use their products, or services.
So what, then if those third parties, their applications and servers were to disappear, then you just use the Alexa app written by Amazon to setup and configure the devices. You sure seem to like to argue about something you have very little knowledge of.
I can use Alexa app and host to add gosund smart devices. Nothing else needed to add devices
I can use Google's app and host to add gosund devices. Nothing else needed to add devices
I can use gosund's app and host to add gosund devices. Nothing else needed to add devices
I can use treatlife's app and host to add gosund devices. Nothing else needed to add devices
I can use Smart Life app and host to add gosund devices. Nothing else needed to add devices
I can use Alexa app and host to turn gosund switches on or off. Nothing else needed
I can use Google's app and host to turn gosund switches on or off. Nothing else needed
I can use gosund's app and host to turn gosund switches on or off. Nothing else needed.
I can use treatlife's app and host to turn gosund switches on or off. Nothing else needed
I can use Smart Life app and host to turn gosund switches on or off. Nothing else needed
Now can you understand that loss of one app and host does not make a bit of difference. Just use one of the others that is compatible. So many wifi smart device company's out there. Some of the companies will even recommend you use a different company's app to add the device to your network because it is easier to use.