[PeterisP]

Trivial things such as injection mold costs (to make a cheap, cost-effective case) mean that low-cost manufacturers avoid adding a button like a plague - we're seeing the exact same layout used by multiple products and in some cases even multiple manufacturers, we're seeing "unused buttons" just as to be able to use the exact same plastic parts instead of having to make a new mold for a new, slightly different part.

Cheap plastic shit is cheap only if you can make lots of them, because the variable cost is low - but as soon as you're talking about small quantities of niche products, the fixed costs dominate as soon as you try to do anything custom physically.