Do B sections exist in RnB?
If you are interested in what makes music tick, you may want to read on. If not, you may find this post somewhat nerdy, and I am perfectly fine with that.
Unlike most other pop genres, a large number of songs in the RnB genre are not built upon the verse-chorus(-bridge) pattern. Listen to Ciara: Gimmie Dat or Mariah Carey: We Belong Together and try to divide it in sections. The songs are built on the same chord pattern throughout. Hooklines do appear and there is quite a lot of variation in the arrangement from one four bar group to the next, yet despite that it is difficult to determine exactly where one section ends and another begins. You could just as well claim that the whole song is one section.
This may be heritage from rhythm&blues in the past. Not sure whether my memory serves me well but at least I recall having heard more songs by Muddy Waters and John Lee Hooker that were groove-oriented rather than sticking to the blues format. More likely though, it may have seeped in from Rap where a groove/beat based structure is much more convenient than a verse-chorus structure imposing limits on the rapper’s ability to improvise.
I claim that the lack of conventional verse and chorus is a major factor defining the genre. Yes, I am aware that this aspect is seen in other genres as well, e.g. some of the electronica genres, and it extends from RnB into Hip Hop and Rap as well.
It is interesting that songs a genre with such a big audience seem to be built like this. Maybe it is related to how the music is used. Please come forward with any opinions on this.

