Except that isn't really why it happened: iot being Internet tied is because it's much, much easier to get devices to work when you control at least one side of the server with skilled professionals rather then your average home user.
And no one has really come up with an alternative: home assistant is good, but it's not for the non-techy.
I will squarely blame IPv4 for some of this: NAT has meant that the key application people might want to use is broken by default (remote device access) without mediation servers.
> it's much, much easier to get devices to work when you control at least one side of the server with skilled professionals rather then your average home user.
No, practicality is not the main reason these unnecessary connections are added. The main reasons are 1. to sell and enforce subscriptions and 2. to collect and sell data.
Is it just easier to get your car seat warmers to work when they can connect to the internet and make sure you're paid up?
HomeKit works great as long as you have devices that support it. The only thing you need a server for is if you want to be able to control things while you're away from home. Control/notification on the LAN is entirely local. Setup for non-technical users is easier, too. You scan a code through a standardized flow, rather than downloading Yet Another App and creating Yet Another Account you'll forget the password to.
Being tied to the internet happens because manufacturers want to be able to watch your usage, sell you ads, and make you buy more stuff from them when they decided your existing hardware is "too old" and shouldn't be supported anymore.