These guys are running really big bars in relation to the size trees they are falling. I'm not sure if it's a pride thing or what, but I wouldn't want any more bar to carry or chain to sharpen than I had to. Maybe with those kind of dollars on a big project, the chain maintenance expense is immaterial.
Different style of cutting out there. Longer bars are less tiring to me. I run 24-28" on 70cc saws and then a 20" on my 357 is the shortest I like to run except for maybe racing in 8x8 or 10x10".