Sure, you can make a basic (and I mean basic) campaign pretty easily with only mapmaking,
but more advanced Campaigns require a bit more work...
If you don't believe me, read some of
these tutorials
[right][snapback]487043[/snapback][/right]
Which have all been done in single maps.
A campaign is much longer, requires alot more work, and is based on melee. Try posting 10 maps in Map Making Assistance and you'd see why this site needs one.
Not to start dissing around at Campaings, but not all of them are Melee based. I've played a few UMS Campaigns that are great. And in the end, it's the same works as a map.
I have not rejected it completely, I said I would fully support my first post in this thread if you could show us that there's enough interest in Campaigns at SeN.