- If your internet if not functioning, the device may or may not function
- If the company that sold it to you closes, it may immediately stop functioning
- If the company that sold it to you decides to discontinue the product, it may stop functioning
- The company that sold it to you may remove or break functionality at any time. It may be left in this state for many reasons.
And then pointing to concrete examples of products where each of these cases happened, which shouldn't be that hard to do, and how long it took to happen in each case (from initial product launch and from last device sold), would result in a lot of people caring about exactly this problem.
In other words, I don't think it's that people don't care, it's that they don't know enough to know they care. It's a relatively new development, compared to items like cars, fridges and dishwashers, which is probably how a lot of people think about their appliance devices.
They also don't care about your company not wanting to support a 10 year old device anymore. They bought and paid for a device and they will expect it to work until it dies or they choose to replace it. In this case it will die, but not because it's broken.
Devices like the Nest, TVs, refrigerators and so on are still expected to last many many more years than something like phones and I don't think a company like Google is capable of committing to something that long term.
The alternative to not make that long term commitment is to design devices that work without a hosted service.
Right now saying that is positive advertising - it won't take much for that to be a negative when people are deciding what to buy.