I believe it has less to do with service providers in particular. There has been a general trend or change in ideals of "female sexyness" over the last 20-30 years. It has also been reflected in the mass media - if not actively transported by them.
The 90s were much more focused on big boobs (think: Baywatch, newsstand magazines, also porn), whereas over the last 10-15 years the attention has gradually shifted quite a bit to bums (in music videos, on Instagram, etc.).
90s Pamela Anderson (who was world-famous for her two "ample assets") has been supplanted by Kim Kardashian as the epitome of the this trend.