All those layers of hard wax start to drag on the snow during the glide phase and slow you down. Then there was the difficulty of trying to match the rather narrow and specific different hard waxes to the changing conditions out on the trail. It is hard to know what to use, when to use it and what goes over what. Even with the ski properly matched to your weight and technique, you still tend to drag the kick wax, slowing you down. Compounding the problem, the friction of the snow on the dragging kick wax caused the wax to wear off quickly.
Durability becomes a problem in changing conditions, long days or races.
Several companies, including TOKO, have recently developed completely new types of kick waxes. They combine compounds designed to improve glide with compounds designed to engage and grip the snow better. The goal was to increase the glide characteristics without sacrificing kick and to improve durability. Because of how new these waxes are, I can only speak specifically about TOKO's system. Talk to your Nordic retailer or your coach about the new generation of kick waxes.