single dotted notes (tremolo through staff) inside tuplets

I have noticed on many scores I have looked at that it was common to create single note tremolos (through staff marking) as dotted notes inside tuplets. As a someone without musical training I am curious as to why this notation was utilized. For example in 4/4 time four quarter notes would fill the measure yet I see instances where the four notes were dotted quarters and to accomplish this they were place inside triplets. Seams like the overall duration of each note would have to be the same as the single note would be the duration of the triplet which would be the same as the undotted quarter. And for dotted half notes, I find these placed in sextuplets. Is this a common notation because I find it in lots of classical scores.