Workstations/servers have forced air cooling that drives a significant amount of airflow over the ram sticks. Gaming PCs don't. I don't think you can make the assumption that heat spreaders / sinks on ram don't help in them.
They're usually perpendicular to the air flow. Bonus points for there being a beefy ATX connector in front.
So maybe the first stick gets some air, but all the others are hidden behind it and don't get much. I think that's the theory why many heatsinks on ricing sticks tend to have a comb design.