It only seems like it's a Smith and Wesson game, it is open to all.
Firearms manufactured by different companies have different pro's and cons.
[IMHO they are all excellent, just different priorites]
The Smiths have a reputation for their triggers and the work that can be done on them. Hense they tend to rule amoungst the target crowd.
The Rugers are very strong pistols, but in competiton no one much cares about this. The Triggers have a reputation for being not as easy to work on.
Oh and another thing, Shooting competitions of all kinds have many 'fashion' victims, also over time you see certain guns or alterations being fashionable for a while and then not.
[One of my favourate sports, IPSC is one of the worst for fashion, you can look at a competitors gun and rig and be able to guess to reasonable accuracy when they bought it (sometimes down to the exact year)]