Good UX patterns are generally those which are recognisable and intuitive to the user.
Checkbox's in the real world are used more in confirmation, or a yes/no pattern. In the real world you can check a checkbox if it applies, but you don't uncheck a checkbox when something doesn't apply. You also don't expect some state change to occur from merely checking a checkbox.
Checkboxes are still used everywhere they make sense. "I accept these T&Cs" for example would almost certainly use a checkbox, not a slider for the reasons I mentioned.
For on / off patterns though checkboxes are less intuitive. When you slide a physical toggle switch in the real world you're typically switching a device from one state to another state - and you typically have the ability to switch back and forth. Checkboxes are not used in this way in the real world so it's less intuitive to use them like this in digital UIs.
I don't think the issue you have with sliders is universal. If you design a slider well it should be very clear what the state is. For on / off patterns changing the colour of the slider from green to red can provide a clear visual hint about the active state.
Checkbox's in the real world are used more in confirmation, or a yes/no pattern. In the real world you can check a checkbox if it applies, but you don't uncheck a checkbox when something doesn't apply. You also don't expect some state change to occur from merely checking a checkbox.
Checkboxes are still used everywhere they make sense. "I accept these T&Cs" for example would almost certainly use a checkbox, not a slider for the reasons I mentioned.
For on / off patterns though checkboxes are less intuitive. When you slide a physical toggle switch in the real world you're typically switching a device from one state to another state - and you typically have the ability to switch back and forth. Checkboxes are not used in this way in the real world so it's less intuitive to use them like this in digital UIs.
I don't think the issue you have with sliders is universal. If you design a slider well it should be very clear what the state is. For on / off patterns changing the colour of the slider from green to red can provide a clear visual hint about the active state.