It is my understanding that she receives royalties through ASCAP every time one of her songs are played.
It’s about publishing rights and literal control. She is only barely less wealthy because of this. And Sir Paul is not going hungry any day, unless he wants to.
There are two royalties paid when a song is played on the internet like through Spodify. The performer gets one and the song writer gets the other. Swift sold her performance royalties. The Beatles sold their song writers copyrights. Each still retains the other. So both are paid their remaining portion of the copyrights. Songwriter copyrights are paid royalties for Radio play, but artists do not get artist royalties for radio play. Artists would get paid for record sales or concerts and internet streaming.
Taylor is always being paid as a songwriter. She is often sharing that royalty with professional songwriters who help her write her songs. She is also getting paid at concerts as a performer as well as the song writer. And of course she is being paid when her likeness is used to sell something like a T-shirt. But she is not being paid for the bigger artist copyright paid on streaming platforms. That goes to the owners of the song “masters”. That is her old production company. Taylor sold that right for cash and in payment to her old production company in hope that they would promote the songs. And they did very well. Their promotion helped make her very famous. And helped her get rich on the songwriting royalties.