Thought provoking question. I'd guess civilian aircraft just don't instill quite the same excitement level in most folks, especially the younger ones. At airshows you don't see many airliners represented, except Paris and Farnborough, then when they do their flight routine it's usually just some flybys and gentle maneuvers.
Military A/C go by at nearly Mach speeds, full afterburners and maneuvers so tight the pilot has to look out his belly button to see where he's going. They can be so colorful and exotic, that it stirs interest just seeing them.
As a pilot of 600 mph commercial aircraft, often I heard passengers say they "found airline flying to be boring, it just seemed like we were hardly moving." At 35-40K feet it would seem that way, and our ops manual stressed the importance of smooth aircraft handling, to enhance passenger comfort.
For a 1:48 military model a tremendous amount of detail can be represented and highly visible, for a 1:144 scale airliner the perspective really changes, not as much scale detail would be that readily seen in comparison.
I build a few commercial A/C models, but much prefer the military types myself. I just consider a camo finish on an F-4, F-105 or F-101 to peak my interest a good bit more. Then there are solid color WWll types with a modest amount of weathering, the Corsair, P-51, P-47 and P-38 A/C hold major interest for me.
Patrick