We already have a "Read all", which to me, makes less sense than either "Accept all" or "Accept and Delete all". I find it particularly annoying when I bid on, say, 20 batches of materials on the AH, and if I don't stay logged on for the next hour, I get 20 different mails that I have to accept and delete individually.
Don't really seem the harm in it but I've never found that necessary at all.
~Sev