Either there are issues with song clearances, contracts with streaming services, or Senior decision makers who are not aware or even Executives who do not care for Elvis.....
If you have watched the "Extras" on the Paramount Blu-ray of " Roman Holiday" of " Paramount in the 50's" there is no mention of Elvis as one of their Stars of the 50s and 60's... the clip ends with a tag of paramount in the 60's and a still photo of The Beatles! That, to me, is someone, who has it out for Elvis. Similarly, there are many institutions, who feel Rock/ Pop music started in the 60's with the Beatles.