Stain powders are expensive. I want to make as much glaze as I can from every gram of this red stain I have at hand. I have weighed a teaspoon of my clear glaze liquid slurry (recipe G2926B). I dried it out under a heat lamp and weighed it again (top left). I have filled those two weights, 8.9 and 4.74, into a spreadsheet I made. It calculates the proportions of water and powder in the glaze slurry. I have filled in "10" for the percent of stain needed. It is telling me I need to mix the stain into 3040 grams of the liquid glaze. That gives me about 5 pints of glorious bright-red dipping glaze. The dipping process enables me to apply it so much more evenly than I can do by paint-on methods (provided that I have the right specific gravity and thixotropy). And, I got this much glaze for about $50 worth of dry materials (vs. $20 for a pint of paint-on glaze).
Hobbyists and increasing numbers of potters use commercial paint-on glazes. It's convenient, there are lots of visual effects. But there are also issues compared to making your own.