It has long been publishing industry practice to seek an endorsement or two from luminaries in the field when publishing new books but, more recently, that seems to have shifted to seeking five quotes, or six, or more. This has increased the (unpaid) workload placed on author-endorsers, but does it sell more books? Does it help readers find books the books they’re looking for?
During my time as an author, I have been both endorsee and endorser, as well as declinee and decliner. I am almost certain to be all of those again in future.