Earlier quoted context omitted.
I don't need to be able to swap a spare battery like we did 15 years ago. However when your battery is old, and drains fast, it's really nice to be able to order a new one and easily change it by removing 4 screws. Not having to perform surgery on your phone, heating it to remove glue, etc.
I'll never forget the feeling when you get an old phone, replace the battery and it's like brand new again. People no longer need to replace their phone every year anymore so being able to just replace the screen and battery makes the device practically brand new.
And if you keep your phone in flight mode when you're not using it, you'll quadruple your battery life or more. Both because the radio is off, and also because apps aren't waking up the CPU to spy on you every few minutes, since they can't transmit it.