Making a texture is fairly simple. You don't have to spend time trying to add 5000 different colors to make the texture pretty. I usually made a simple design with 2 or 3 colors, then add some noise or blurs.
speak for yourself. I recently done and used a mod called ddb doityourself decorative blocks which lets you make your own blocks and I make my textures all 96x96 and I set it so it uses 4 different textures, top,bottom,sides, and front. Now I made 16 colored grass blocks + rainbow one * that by 4, that equals 4*16 = 64 images. Not easy to do. Granted all I had to do was recolor, but next step is I need to color the logs, stairs, slabs, and planks. All the same set up. So 4 images, 6 types of wood, 16 colors, 4 versions = to much and not enough time.
This alone is why I DESPISE "HD" textures. The more pixels there are, the more time you gulp down. That's why virtually every modder ever uses a 16x16 template when making textures for blocks.