Ross and Rachel were together for a while on Friends but then they broke up so we could root for them all over again. Ultimately, they had a daughter together and ended up back together just as the show was coming to an end.
Meredith and Derek were a couple but then they broke up when Meredith found out Derek was married. Week after week, we hoped they would reunite which they finally did.
Penny and Leonard were together for a while on the Big Bang Theory, then they broke up and are now back together, which ties in with the rest of the show where each character is dating or marrying their significant other, with the except of Raj :( Just a side note, at one point Johnny and Kaley dated in real life.
But really, when these characters finally end up together, even though it's what we all wanted, it causes the show to lose something. Case in point; years ago there was a TV show called Moonlighting with Cybil Shepard and Bruce Willis. They ran a detective agency and the chemistry between the two was so great, it leaped off the screen. Everyone wanted them to get together but when they finally did, the show went off the air.
Then we have Joanie Loves Chachi. Chachi pined for her for years on Happy Days. They finally got together and Happy Days was cancelled. But don't fret, as they got their own spin-off series which lasted for one season and has been called one of the 25 Biggest TV Blunders. The need for them to get together was already satisfied so we no longer cared what happened to them, as a couple. We didn't tune in to watch them fight and argue week after week.
Remember the show Who's the Boss with Tony Danza? When Tony and Angela finally admitted they had feelings for each other, the show went off the air.
Another show that comes to mind is Dr. Quinn, Medicine Woman. Jane Seymour had a thing for Joe Lando, a ruggedly handsome Indian whose screen name was Sully. I also had a thing for Joe Lando as did millions of others :). For many seasons they played cat and mouse and finally when they got together and married, the show went off the air.
Just recently I was watching Joey and Melissa, a family friendly comedy that airs on ABC family starring Joey Lawrence and Melissa Joan Hart. It is a cute show where Joe works as a nanny for Melissa, who is on the city council. The last show of the season, they hooked up. Where will it go from here we don't know but truly, the premise of the show is ruined if they become a couple.
So I guess what I'm saying, on screen chemistry is a wonderful thing. It makes us tune in week after week and that is what keeps our favorite TV shows on the air so be patient and enjoy the ride.
R. K. Avery