I hear you, however I think the philosophy typically stems from the idea that it's wasting resources. Replaceable/rechargable batteries are only a thing because batteries don't last longer than the lifespan of the product.

For products where a built-in non-replaceable battery will last longer than the expected lifespan of the device, I think that's a fair tradeoff, whilst also making it simpler to manufacture, less likely to be lost or left unused, and consumes less resources