Because then the coffee shop has to curate it or the band needs to market to the coffee shop.

Incentives are mismatched here - the indie band benefits from being noticed and sought out, the coffee shop wants to set a vibe without distracting or irritating anyone (which music can do simply by repeating, if you don't curate a large enough collection).

So unless your playlist is, like, part of the product you're selling (which it is for a number of coffee shops to be fair), you just look for something like "10 hours of lo-fi beats to study to" and throw it on.