Yes, your preference probably is a better one technically, but when looking at a business model, the 4 x 5 (or 5 x 4 on the other side where they are located) probably does look better from the standpoint of being able to sell enough to make a profit. Well, at least some profit.
At this time, I am not sure that I am ready for an 8 x 10, but a 4 x 5 field camera is workable. Also transportable.