I think there are benefits. They are just unstated / unpublished. Like all the FAs and GAs who will know you and personally treat you better. Like the res agent who will see that you have 150k miles and bend the rules. Etc.
DL bend the rules when it comes to reservations agents were they to notice that I do well over 150k miles? Not on an award ticket, not on my multi-airline paid tickets, at least no more than before.