Never-mind that passports tend to be expensive (relatively speaking, for the average person), many countries don’t issue passports for a variety of reasons: the UK will refuse to issue - or confiscate - passports of football hooligans specifically - or suspected terror-tourists, I’m sure other democracies have similar policies, let alone more authoritarian regimes.

In the US, it's not mandatory that you get one. Many people don't get one unless they plan to leave the country. This is especially true given that many driver's licenses are valid as a form of federally recognized ID here (i.e. you can fly domestically or whatever).

The people "not eligible" for a passport are those too poor to afford the process or those without any other reason to get one.

That's just not true.

Only 42% of Americans have passports. A passport is not in and of itself required to live in a country, just to leave one. It's also expensive -- out of reach for many lower income folks. All you really need to get UBI is proof of citizenship, like a birth certificate.

Many refugees have no feasible means of obtaining a passport. Many people are too poor to pay the bribes that would be necessary to get a passport they are nominally entitled to. Others may find it impossible in practice on account of being of the "wrong" ethnic minority.

E.g. Tibetans, who are not allowed to travel outside of China...