"what ASCAP has already negotiated with songwriters, composers, lyricists and music publishers" There is a huge difference. ASCAP represents ASCAP members, who

"what ASCAP has already negotiated with songwriters, composers, lyricists and music publishers" There is a huge difference. ASCAP represents ASCAP members, who choose to join the organization. ASCAP then becomes a legal agent regarding collecting royalties for the musician. Many musicians join BMI instead. But crucially, many do not join either organization. Neither organization is a publisher, they are a music licensing organization that works for its members. For this to be comparable, ASCAP would become the representative of musicians whether they want that or not, and would be able to publish musician's works without permission. That is certainly not what ASCAP does now.