Chemistry. They have SO much chemistry. 팬 went CRAZY for BR way 더 많이 than Ted and Robin. And even when they tried to break them up people still wanted them together.
They also have an incredible back story and they're like best 프렌즈 which..I don't know...makes them RIGHT together.
I know a lot of people hate them though. But the people who 사랑 them together won't rest until they ARE together.
Me? I wanted them together since "Zip Zip Zip" when all that TR crap was going on lol.
Also, if you're looking for theories on whos the mother, 또는 season 7 spoilers:
link is my blog :)