Washing colored clothes

Maybe it's a silly question. But I just do one load of laundry (everything mixed together - no color separation). Because I don't have a lot of black clothes I wear at one time. Like I end up with maybe 3 black colored items. It's such a waste to throw 3 items in the washer and dryer. I don't feel like waiting for the next pile of laundry to have more black colored clothes to wash together. Same with white clothes. It just makes more sense to me to wash them all together. So my question is, do people really wash just a few items of clothing at a time? Or even wait a long time to wash until you get enough of the same colored item clothing to wash? (But I don't wanna wait!! I wanna wear it already.)