I don't get why anyone would want a device connected to the internet at all, in the first place.
Some might like the convince of an IoT device like the Echo. That's a personal choice. Properly developing both sides of the device spectrum should improve quality and security.
This idea that we shouldn't even consider connecting tools to the internet because the internet is scary and dangerous feels like a knee-jerk reaction to me. I believe there is a right way to build these tools where the risk added is minimal to non-existent. Refusing to pursue this tech at all because some people do it wrong just feels like ludditism to me.
Imagine what would have happened if people abandoned computer technology after the first few viruses were discovered.
My issue with the current trend is that 'IoT'/Internet-enabled is a way to both sell a product, and then effectively rent access to it via the 'cloud' interface. If you stop paying, your device is (mostly) useless. If they stop supporting it, your device is (mostly) useless. The actual whereabouts of any data produced by your device is probably unknown, as is its security and usage.
It's the same tired old "If you're not paying..., you're the product", except that you're actually paying.
Many of these abuses are much harder to do if you don't expose your exciting new Thing of Internet directly to the entire global communications infrastructure, but then we're back in the bad old days where people had to use software that wasn't a thin client in a browser[1].
I'd really really like a LAN of Things, or a VPN of Things, that still functions after your service has gone bankrupt or sold their souls to Oracle or something. But of businesses, especially those riding the wave of 'your data is feedstock to our deep-learning quantum magic pixies, and we'd never ever sell it all for a cheap buck[2]' would find it much trickier if that sweet sweet data wasn't coming their way.
Development & distribution, as well as actually charging for for things, become harder problems though, which means everyone wants to head to the promised land of *aaS, where A/B unicorns frolic in the fields and green/blue munchkins guide your clueless users down the yellow brick upgrade pipeline.
[1] Only mostly sarcastic. [2] unless someone offered
Even taking these benefits as given, neither of these things need to be connected to the internet, especially not directly. A fitness application that stores your data locally and potentially offers to sync your data across devices, sure, but for these things you describe (and most IoT things, mind you), the benefits of connecting them to the internet are minimal at best.
I don't think anyone is suggesting that IoT devices store their data in some opaque format that can only be accessed on-device. However, for most of these things the model is to treat all IoT devices as dumb terminals for a cloud service, which unnecessarily has deleterious effects on your privacy and security and makes your device's utility dependent on the provider's infrastructure.
I'm extremely selective about what devices on my network actually get internet access, and IoT is like leaving your front door unlocked (and wide open) in the worst neighborhood you could possibly imagine. I'm kind of blown away people allow these things into their home.
If you want me to put your shitty IoT device in my home, open source it and then we'll talk.