Bar associations are struggling with declining memberships these days, Barry E. Fields of Kirkland & Ellis LLP said.Some people, he said Wednesday at a Standard Club luncheon where he was installed as president of the Federal Bar Association’s Chicago chapter, suggest the new generation of lawyers thinks voluntary bar groups are out of date.Others speculate that lawyers don’t see advantages to belonging to a bar group, Fields said.He said the FBA’s Chicago chapter, which has about 600 members, &ldquo …