Why should that be the case, thats like saying we are not going to try in the league as we want to win a cup.
Success in any form is what Fans want,from league titles, cup wins, European qualification, group stage football, playing effective attractive football, etc to avoiding relegation.
Yes other clubs have won trophies since our last success in 91, but we have been successful in other ways, fairly regular European qualification we have played in the champions, Europa, and conference leagues since 1991, been a premiership team for the last 40 years, so is one cup sucess for say St mirren in that period equal to what we have achieved as well, fo me no it has'nt