Will Meredith and Derek ever be together? Much as viewers might hope so, television history offers evidence to the contrary.

Last week on The West Wing, NBC's award-winning and long-running political drama, former White House staffer Donna Moss hooked up with her boss, Josh Lyman (pictured). The significance of the event was that Moss and the former Deputy Chief of Staff had been pining for each other since... 1999. That may be some kind of record. While it's an extreme case, a column on Slate.com says it's par for the course for TV shows to keep perfect couples apart. It's a tale as old as time. Or at least the '80s.

On the classic sitcom Cheers, the love/hate relationship between Sam Malone and Diane Chambers (then later Rebecca Howe) was a central theme. On spinoff Frasier, Niles futilely pursued Daphne for many seasons. Friends saw Ross and Rachel hook up and break up so many times it became absurd. Even now we see palpable sexual tension between Kim and Pam on The Office, as well as with Gil Grissom and Sara on CBS' immensely popular CSI.

It's a formula for success, no doubt about it. Having introduced the young Dr. Grey and Dr. "McDreamy" Shepherd as a couple early on, and subsequently driving them apart with the arrival of Derek's estranged wife, Addison, it looks like the Grey's Anatomy writers are following this path.

We so used to the idea of couples we love waiting multiple years to get it on that we don't even give it a second thought. Why is this so commonplace? How did the slow-mo courtship practically become a must for hit TV? For one thing, it makes for easier execution among writers and actors. Many say it's difficult to generate and sustain sexual energy between two characters ... when they are actually together. This makes for an interesting social commentary about our culture in general. Do we, as Americans, always want what we can't have?

Consider this theory as it applies to Grey's Anatomy. Meredith wanted Derek from the beginning, and still does. Because she is the eponymous and central figure, we want her to be with Derek, too. It's clear that at least part of him wants this, too, in spite of a sincere effort to repair his troubled marriage. With Addison on the show, the writers have created a believable scenario in which its two stars can continue to love one another -- and be kept apart -- indefinitely. Because it uses the traditional blueprint for success, but throws in a new ethical wrinkle (whether or not Derek should stay with his wife), it's pure genius.

This isn't the only time Grey's Anatomy has played the drawn-out sexual tension card, either. George lusted after Meredith for, oh, 27 episodes before putting himself on the line. With the arrival of Denny, Alex and Izzie appear to be dead as a couple, but that plot line took a year to run its course. The romance between Cristina and Dr. Burke is an anomaly. With two brilliant, complex and seemingly mismatched characters (who are also secondary to the Meredith-McDreamy plot line), it's more fun to watch them together than be apart.

Regardless, the brains behind Grey's Anatomy know what they're doing. With a great cast and a new spin on themes that have made past TV series successful, don't expect the drama to cease anytime soon.

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.