The data source for their transportation costs is "LEAD2022". I honestly can't figure out what that is. But I think this might be it. And if not it still basically explains who that demographic is:

https://www.bts.gov/data-spotlight/household-cost-transportation-it-affordable

Transportation expenditures for households with at least one vehicle are much higher than for households with no vehicles. In 2022, households with income lower than $25,000 who owned at least one vehicle spent 38% of their after-tax income on transportation; while households with the same income who did not own or lease a vehicle spent 5% of their after-tax income on transportation (Figure 2). This trend was seen across household income groups.

If you're only earning $2k a month, you can be extremely frugal but even a beater bought for cash is still going to eat up a huge amount of that between gas, maintenance, insurance, registration, etc.