Because it's not obvious at all from their commercials, and that's how most people come to know about this shady org.

In CharityWatch’s view, the Kars4Kids ads deceive potential donors by failing to inform them that donated cars will benefit a Jewish organization and kids of Jewish faith. Furthermore, the youth programs Kars4Kids supports promote an Orthodox Jewish lifestyle, which CharityWatch believes compounds the deception perpetrated by the Kars4Kids ads

https://blog.charitywatch.org/costly-and-continuous-kars4kid...