Nope, no reason at all, unless you just really want a 7 weight. That's an unusual rod weight, sort of the 16 gauge of fly rods. It sits in a sweet spot that those who prefer, really enjoy. Others will defer to 6 or 8.
But if you're also headed for an eight weight, that is further reason to go with a six. Loads more lines available for sixes is another argument.
"have fun with this stuff"
in memory of Big Dale
RRhyne56, Flyfishing warden