Because, surely, if they spen longer on it, it will be, overall, a better quality game.
I disagree, to a point.
First of all, many games get stuck in "development hell" such as Duke Nukem Forever and Daikatana. If they are released, it is years away from the projection, and the game is ALWAYS sub par. TES V is not there. Falling into development hell takes a major screw up, avoidable or not, such as lack of funding.
But a game which is developed for more time than is necessary suffers the same effects. If you wait too long to release, you have to update your initial progress because good technology in 2010 is old hat in 2012...but that process only adds more time to completion, and a game that could of been made in 3 years, was planned for 4, and needed 5. That's money, in salaries and sales.
Everyone assumes that the more time they spend, the better game they will make. Obviously there is a certain time frame needed, to build, test, and polish, but that is why the building should be done as close to the projected date as possible. Because once it's finished, you can test it, and testing a game is directly related to the amount of content inside of it, and the polish time is directly related to the amount of bugs detected in testing. If you lengthen development time, you increase both of those factors.
So I would light a fire under Bethesdas butts. Get it done, out, made. Test it, fix the bugs, release it. Here is where people say "well what if it's missing so and so a feature, or they didn't do a good job doing this, they needed more time" The best way for them to figure all that out is from feedback, and the quicker they are making games the quicker they can make adjustments to each one in the series.
So all of you who think 6-7 years is a decent time frame for a game, think about this: No amount of time makes the perfect game. But if they do screw up something, it's going to be another 6-7 years before that gets fixed. And so on.