Other reasons are: the transponders that ATC (and other aircraft) interrogate report pressure altitude (uncorrected, meaning using 29.92 inHg as the standard).
A sensitive altimeter can be had for a few hundred dollars and requires no electrical power (unless lighted) and basically no service throughout its life.
To your last point, anywhere it matters (below the flight levels), pilots are using a local altimeter setting on the altimeters, often from the ATIS (automated terminal["airport"] information system) or from ATC. Of course, for takeoff, it doesn't matter. You're generally climbing at max available power or are doing a reduced power takeoff in aircraft so certified and on runways without obstacles to worry about.
On approach, you're typically following a precision approach path provided by a radio signal (ILS includes lateral and vertical guidance beams) or that is GPS-based (where you have similar navigation performance levels provided by WAAS augmentation). There are non-precision approaches where the altimeter setting is more critical, but I can't recall the last time I had to fly one of those for other than training purposes.