Musical collaborations between artists who normally do their own thing have been around for a long time. Back in the 80s collaborations were rare enough that when one did become a hit, it was a big deal.
The trend began gathering pace in the 1990s, and hasn't stopped. Today, about 35 percent of the Billboard Hot 100 songs are now collaborations, up from just 5 percent in 1990.
There are a number of reasons for this, but the biggest might be the rising popularity of hip hop.
Music: Camila Cabello (feat. Young Thug) "Havana", RUN-DMC (feat. Aerosmith) "Walk This Way", DJ Khaled (feat Justin Beiber, Quavo, Chance The Rapper, Lil Wayne "I'm The One", Taylor Swift (feat Kendrick Lamar) "Bad Blood", Bruno Mars (feat Cardi B) "Finesse (Remix)"