All your points cover network access and physical access. But that's not the major threat to computers: the major threat is what is run on the computer during normal operation.
- email attachments
- programs
- and a ton of what happens on your browser
Your browser and email client might be up-to-date, but what if they have a vulnerability that doesn't have a patch? (this happens more than we like to realise) Then your OS is wide open.
Security is about defense-in-depth. Technology is a stack of layers and so is security. If you weaken one layer, you are relying all the more on the few layers left to be rock solid. And playing Russian Roulette.
The advice from all experts is to run only up-to-date and supported software. Sure, there are ways that you can "strengthen the stack" when you need to have one weak layer, but home users are not normally set up to do that.
The better option is to run another OS that is up-to-date. Don't want Windows 10? Then look at alternatives.