Usually it is desirable to have a writer’s signature in a book. And often, a personal message in the book can be desirable, if the writer and recipient are both long dead.
On the other hand, it is generally not desirable to have a book with a personal message of recent date. There’s no real reason… other than than it makes collectors deeply uncomfortable, and that it makes it impossible to ever show your copy to the author. Nobody wants a book to make them feel like a social stumbling block, surprisingly enough.
I mean, there’s your author showing heartfelt gratitude and love for someone else — and then that special someone turns the book around on Amazon? Pretty cold for the writer.
On the other hand, it makes one feel protective of the author of even a bad book.
(The title is a classical reference, as Instapundit/Glenn Reynolds would say, to Kipling’s poem, “Mary, Pity Women!”)