There are hundreds of music producers but unfortunately only a few that provide completely legal music, so maybe that's why only a few of these are being used?
That's right - you need to get permission (a license) from BOTH the master (the artist who recorded the song) and publishing (writer/s of the song) sides. So when you hear artists like Arianna Grande, you must ensure whoever is providing you with the music has got these permissions. Very often...