- Waterproofing. Fewer seals means more resistance to water ingress.
- Compact size. Standard battery sizes rarely fit thin or irregular designs.
- Better battery life. An integrated battery can be designed to fill all available spare space in a device.
- Cost. Integrated batteries involve fewer connectors and parts.
- User satisfaction. Users often blame original manufacturers when the problem is actually poor quality 3rd party batteries. This was extremely common back when most laptops had removable batteries.
And why do arguments in favor of removable batteries apply to phones and laptops, but not headphones, vehicles, cameras, etc? Just let people buy the devices they want. There’s no need to have the government force people to use things they dislike.