Having spent a fair amount of time smoking cutty shaped pipes and "tavern" pipes (basically a churchwarden-length cutty) I have my own theories about why they're shaped the way they are. Here's an example of a briar tavern pipe. This is pretty close to how the old clay pipes were shaped back in the day. This is a Ropp:
First: the fact that the bowl is canted, and roughly egg-shaped means it fits comfortably in the closed palm of my hand—(I love the hand-feel of an egg)—and when I hold the bowl in my hand, the stem is oriented directly towards my face. I can hold my forearm and hand in a position of almost maximum relaxation, especially if I'm sitting down (say at a table, in a tavern). I don't need to lift my hand up towards my face. I said this in a previous thread, but the way I see it is, it's not that the bowl is canted away from the stem, but that the stem is canted away from the bowl, towards your face. I think cutties were designed the way they were for well-considered, practical reasons, and the design has not been improved upon. (YMMV!)
Second: if I hold the stummel between my index and middle fingers (the way I would a cigarette or a cigar) at the transition, the spur sits snugly against the inside of my 1st knuckle (at the base of my middle finger.) I can hold the pipe this way rather mindlessly and walk around. This position also comfortably orients the stem towards my face. It gives me a very secure grip, so I think the spur serves a purpose beyond allowing the pipe to (possibly) sit. (The wutty design is different/unconventional. I don't think it would be as comfortable to hold, but I've never owned one, so maybe I'm wrong on that count. The fact that a wutty can sit firmly on your desktop is kinda cool though.)
The third, historical, point is that clay tavern pipes were made with long stems because they were designed to be rented by tavern patrons. You could grab a beer and order a bowl of tobacco, back in the days when that was a more rare commodity. (People didn't necessarily own their own pipes, or have a supply of tobacco on hand.) The pipes were disposable, and meant to be reused by multiple customers, so rather than cleaning and sanitizing the slobber off the stem, the end could be snapped off and rented to the next person. Once the stem was down to a nub, the pipe would be discarded. So you'd see cutties with all lengths of stem from long "churchwardens" down to stubby little numbers. An eminently practical design, through and through, IMO.
Here's my latest cutty which arrived in the mail yesterday from France. This is a Ropp stummel, finished, and with a hand-cut stem, by Belgian artisan Bruno Nuttens. All proceeds from the purchase of this pipe go towards a charity which is trying to save the old Ropp factory in Baume-Les-Dames, France.
This is the most canted cutty I've owned. When I hold this at a comfortable angle, the bowl points downwards. Any practical reason for this? I couldn't say. Smokes like a dream though, right out of the box. Love it!