Sometimes, if you do a quiz when the student has been working on the same problem in the same lesson, they will be able to answer straight off.
However from your response, I assume you mean a quiz on the topic when the student is cold to the subject (as in, they've not warmed up on it after the homework topic).
Are you going to tell me that you have a class of 30 students. you're going to quiz each student 5 to 10 times on mathematics questions verbally? Or get them to do it on paper, with 20 different questions and you mark it correctly for them?
Sometimes teachers does do things that seem a bit "lazy" but there are reasons for them doing it. If you ever want to find them out, the teacher should be more than happy to explain it to you in a reasonable manner.
Sometimes, they are constrained by educational decreed that imply they must set certain workload by a certain amount or face disapproval from management. What most people don't realise with teachers is that they face a LOT of red tape and a lot of governmental pressure which runs against what is actually good for the children or not.