Car insurance is legally mandatory if you drive a car. If your income is predicated on being able to commute by car (as it is for many Americans, though hopefully a trend toward remote work will ameliorate this somewhat) then your insurance is no more optional than your gas.
People also talk about smartphones as though they're a luxury item, but for most intents and purposes owning one can be viewed as required. Tons of services, including your bank, require a cell phone for authentication, if not to use their services at all. Everyone from your boss to your spouse has an expectation that you can be reached most if not all of the time. I try to avoid being reachable at all times, but this is a luxury I can afford because I'm relatively well-off and technologically adept, and I still can't get around 2FA requirements for everything.
So like, if that stuff is bought with "disposable income", is rent?
And the median and average for disposable income is a lot higher in the US than in Europe. US disposable income is only comparable to the most affluent nations of Europe: Norway, Sweden, Denmark, Switzerland.
Americans waste an enormous amount of money on consumer garbage. Until recently it was very common for households to have $150-$200 / month cable or satellite TV plans. It's still common, just slightly less so thanks to Netflix etc. $200-$300 family smartphone plans are common.
Americans also flip in and out of cars frequently, losing huge sums of money doing it. And they buy ridiculously over-priced new vehicles, which they keep for relatively short periods of time.
Please please don't redefine economic terms to suit your intuitive belief about what a word "should" mean because you are wading into an area where you don't know the agreed upon terminology. That impedes communication.
If you want to refer to income after paying necessities, then this is "discretionary income".
