Consider the two images below: The first has many more colours than the second, and you can imagine how much extra effort it would involve to apply so many extra gradients from light to dark.
As seen in a recent Henk Nieborg interview, he confirms that the need for speed outweighs the luxury of applying many-coloured gradients.
Quote by Henk Nieborg:Everything needs to be faster today. Most jobs i get need to be done ASAP for some reason. It also shows when you look closely at my pixels from the last few years. I do not use that many different tints (gradient) for a single color anymore. For instance i used about 4-6 different tints on one color for Contra4. I used about 16 tints per color in Lomax. That was a little bit overdoing it really looking back on it. Anyway, Reducing the amount of colors is saving a lot of time. People are still happy with the result so why not.