You can have the batteries swapped out though. I had the battery on my 6S replaced twice. The first time I got it for free because of the degraded performance issue and even the second time was very well priced ($60??) and have the phone a new wind. However, now the power connector had become very loose and disconnects randomly when moved wrong. I probably could have that fixed as well for cheap, but want the new camera. On my recent vacation I took almost no photos because I wanted my wife to take all the good shots with her XR Max.
I'm on the fence though because I use ApplePay a lot and cannot imagine using that with FaceId and I also am somewhat attached to the audio jack. I don't want to carry headphones for my phone and another set for my Switch when on a long trip.