All advisory calls are operator specified. My last airline had no height calls on the 737 - it was all done by pilots, and I still find the height read outs a little annoying when landing.
The 2500 foot call is specified, or sometimes manually applied as an SOP, as it is below this height that mode one "Sink Rate" calls (at rates of descent of roughly twice the radio height) become active. It's a trigger to be aware of your sink, and control it so that a GPWS call isn't made.
I have seen rad alt displays (old ones, with a needle and dial) which ran above 10,000 feet. Why? They were used for Pressure Pattern Flying - a navigation technique in which accurate heights above sea level (on over-water legs) are compared to changes in pressure (from the pressure altimeter) and the difference can be used to calculate your drift angle. The calculation markings for this can still be seen on Jeppesen CR series flight computers.