As a professional watchmaker, being able to buy fresh, high-quality batteries one or two at a time is perfect for my business model. At least 95% of my work is with vintage mechanical watches. Having to stock batteries for the occasional need makes no sense. Stocking ties up money and space--then there is the shelf-life issue.
For those who change batteries on a regular basis, buying in quantity and stocking dozens of different numbers makes sense. For me, the ability to buy one or two batteries and have them quickly and economically delivered is ideal.