Yes, it’s disgraceful.
Maybe, over the past few years, she’s decided that it’s distasteful, given her position, to be displayed in that way. She may have been asked, but declined - we don’t know.
(I’d certainly decline, were I in her position. I’d think that it would be cheapening the Presidency.)
She has always done an excellent, elegant job as First Lady, and that’s something far more important - and requiring more dignity - than just being a ‘cover girl’. Melania seems to understand that.