Not just because they aren't easily upgraded... when was the last time you saw some other turntable, say a Sota or a Linn or a VPI with a "Music Hall Tonearm". With the Rega, at least, you've got a absolute winner of a tonearm that can be used on MANY other turntables with great result. And, since these two brands share similar price points, it make the Rega more of a contender.
Beside that, the "whole comes with a Goldring cartridge" thing is just so universal and not everyone wants a Goldring cartridge.
Besides the Music Halls and the Regas, I think the VPI Hw19 series is a fantastic buy at the prices these are going for these days. A truely great turntable, in build quality and sound quality. So I agree with the previous poster.
Good Luckc