Very simply - Michael Jackson was the person who put up the money when The Beatles' back catalogue was sold by EMI Records in the mid-80's. For reasons not specified, the remaining beatls did not step forward to claim their heritge, causing severe strain in the relationship between Paul McCartney and Jackson. this resulted in Jackson paying a higher royalty rate to Lennon's widow Yoko Ono when songs he owned were played on radio, than to McCartney. Rumours persist that Jackson's ongoing financial difficulties may result in the sale of his percentage of the Beatles, works to his parent company Sony Music. The remaining Beatles, and Yoko, do have considerable control over the remainder of their catalogue, and I am sure various limitations on usage exist - have you noticed that no original Beatles music ever appears on any CD compilations, or in any adverts.