The vast majority of people prefer to also use the car privately, and pay the tax (which is reasonable, if taxation is reasonable).
Cars that keep rotating between drivers are not subject to that (but exact record keeping of driver and trip required to avoid tax)
Similarly, employer provided phone subscription is assumed to be partly private use (50% of monthly subscription cost considered a a taxable benefit iirc), not sure what hoops you need to jump through to prove it is not private use at all. (But phone plans are cheap - excellent domestic plans are $10 or so)
Obviously this only happens when the equipment you get can plausibly be used for personal purposes. Such as a company car.
> What happens if you can't afford that tax then?
That's extremely unlikely.
so you get charged a tax when an employer gives you equipment required for work? What happens if you can't afford that tax then?
This feels very wrong - taxing someone for a potential benefit when it is not proven that such benefit exists.