Much of this is due to cultural listening habits for example America vs UK.

If you look at the top albums in the US on Billboard over the last forty years there is little variation and most are in the pop/R&B genre with albums holding on for weeks at the top.

Whereas in the UK the top albums change weekly across multiple genres. The BBC radio played a massive part in exposing a country to multiple genres and styles of music. The UK still often breaks alternative American artists and new genres (house/techno).

In the US, listener habits have always been segregated on radio, so while marketing does play a part American audiences are very specific when listening to music.

There aren’t enough Americans that have listening habits across multiple genres to grow songs from the underground to mainstream. Overall quite conservative.