Friends is a sitcom about 5 people: Rachel Green, Ross Geller, Monica Geller, Joey Tribbiani, Chandler Bing and Phoebe Buffay. Season nine begins with Ross and Rachel living together as roommates with baby Emma. Monica and Chandler try to conceive a baby of their own but find out that they are unable to, due to health restrictions. Phoebe begins dating Mike Hannigan, and chooses to be with him over her ex-boyfriend David. Rachel and Emma move in with Joey in the middle of the season, and Rachel develops romantic feelings for him, while the rest of the 'friends' try hard to get Ross and Rachel back together.
The writers finally reached the point where they apparently had tackled all the possible road blocks to Ross and Rachel getting together, opting for a hail mary of a story arc in which Rachel falls in love with Joey. No, Friends. No. Bad Friends.