Don't citizens from other countries (non-US) need a passport? Aren't the passports looked at for previous travel destinations?

It would depend on where a person was from, and what kind of agreement that person's country had with other countries. For example, I am from an EU country and am free to travel to any other EU country without having to get my passport stamped. When flying then obviously you need to book an airline ticket which requires passport details as well as other personal details, so there will be some form of paper trail in that situation. But my passport is not always electronically scanned by immigration and, if I were to drive across Europe, there wouldn't necessarily be any record of that at all. At best my passport might be visually inspected at borders, but largely not. So, if thee are any countries that have any such agreements with or between African countries there is no guarantee there would be any record of where a person has been. Some people have two passports, in order that they can travel to a country without immigration offers being suspicious of certain stamps (for instance, if I had 2 passports, and had travelled to Israel, I wouldn't want to travel to an Arab country with an Israeli stamp in my passport, so I'd use the other one if I ever did). So, in summary, passport scanning isn't a fail-safe way of checking where someone has been.

it's scandalous

your asking if people do their jobs. of course not, the pay is the same.