I tend to agree with c9h - playing lots of razz won't make you a better hold 'em player. It could make you a better razz player though.
To some extent, I think the suggestion that you need to be good at a variety of games to be a solid poker player is a hangover from yesteryear when a lot of different games were played, and hold 'em wasn't even offered played in some casinos
. So if the only game on offer was stud and you weren't any good at stud, you weren't going to get any action.
These days, there's absolutely no shortage of NLHE action. You could go your entire poker playing career profitably playing just that one game.
I think the real advantage other games offer these days is the additional edge you can get over your opponents by being good, particularly at the lower limits. Hold 'em action is ubiquitous, but the flipside of that is that there's a lot of decent players out there. If you can get really
good at razz, for example, you might make more per hour than playing the same limits at hold 'em because you could in theory build up a bigger skill advantage over your opponents.
The other reason for playing them, of course, is that they're fun. I don't kid myself, NLHE is my most profitable game. But that doesn't stop me playing razz or omaha for fun occasionally.