I use one because of kindle unlimited, it's nice to have a big selection of books I can just hit 'read' on right on the kindle store.

I don't know if the alternative e-readers have an equivalent store? Tracking down epub files on my PC then transferring to the device multiple times a week sounds a bit frustrating as an alternative.

Also they support kindles for a long time, my kindle oasis from 2016 that I bought used still is supported, and the things battery also somehow is still in good shape.