I mean, the 6a still has 3 years of support left so whilst it is older it is hardly at the end of its supported life.
Not everyone can change a battery in a phone, I can but I would still rather not do it on a phone that isn’t really anything special and whilst yes they could feasibly last that long I think in practical everyday use application by the time you are getting to three years of daily use it will be beaten up and physically not in great shape any more for your average user.
Jeez everyone carries a lot of shit in their pockets.
I carry my bank card in a side pocket down by my right knee and occasionally keys in the front left pocket.