Does any remember the DEC Alpha? Windows NT 4.0 was ported to it. The Alpha was a 64-bit RISC processor. (Reduced Instruction Set Computer) An ARM is just an Advanced RISC Machine. RISC architecture has an instruction execution advantage over CISC (Complex Instruction Set Computer) that is what Intel is famous for. Although they did have a i860 and i960 RISC which many of them were for embedded military systems.

Other RISC systems were from Silicon Graphics, with their MIPS processor were used for 3D graphic processing. RISC has shown that it has its place in the computing world time and time again.

My personal appeal is their low power requirements and compact designs. Obviously cell phone manufactures like it too for the same reasons.