Well, on the other hand, why not? And why limit oneself to a Century Graphic? If one wants to use 2x3 Graphics and shoot an interesting range of focal lengths without taking extreme measures, one needs a short one (Century or 2x3 Crown, both have minimum extension of 34.9 mm, will focus a 35/4.5 Apo Grandagon to infinity with mm to spare) and a long one (2x3 Pacemaker Speed Graphic). For focal lengths up to around 480 mm, given a short and a long 2x3 Graphic cobbling up a tandem Graphic isn't that hard.
You shouldn't compare what can be done with a 2x3 Graphic with what can be done with a 4x5 or larger camera. Compare with a 35 mm or medium format camera. Years ago a friend who was very proud of his Pentax 645 came by. I showed him some 2x3 trannies. He remarked that next to them his looked pretty punk. You have to remember that 645 is half frame 2x3.
Re cheap lenses for 2x3. Um, er, perhaps if we're thinking about ancient tessar type normal lenses, some of which are outstanding. Decent wide angle lenses for 2x3 can be quite expensive; if you don't believe me, price a 35/4.5 Apo Grandagon and don't forget the center filter. Longer lenses, with the exception of some elderly telephoto lenses for formats no larger than 2x3, are all for 4x5 cameras. They don't have to be horribly expensive but they can be.
To get an idea of what's possible, see
http://www.galerie-photo.com/telechargement/dan-fromm-6x9-lenses-v2-2011-03-29.pdf. I've added a few lenses since that piece was published. The most outrageous is probably a 45/9 CZJ Goerz Dagor that barely covers. On the whole a 47/5.6 Super Angulon is much preferable.
There are also real view cameras for 2x3 that offer movements. I don't care what lying enthusiasts and people who've never used the cameras say, the only generally useful movement that 2x3 Graphics offer is ~ 19 mm of front rise. I have a couple of 2x3 Cambo SCs. Nice cameras, heavy, and the standard cases for transport are bulky. But I can do things with them that aren't possible with my little Graphics.
One last thought. The original post is misplaced, 2x3 is usually seen as the largest medium format (but how about 6x12, ... , 6x24?), not as the smallest large format.
