The ultimate design goals of the site are still constrained by its Stack Overflow heritage: It's a system designed to answer the current questions being asked, and floating old questions back to the front page regularly tends to interfere with that.
Popularity inherently falls off as questions age, and even our best early questions are unfortunately in the "long tail" now (with apologies to Chris Anderson).
Theoretically if people are interested in the content of older questions they can find them - Google likes us.
There are two exceptions to this:
- If these questions are edited or get a new answer they will be "active" which will bring them back to the default front page. (If there is no real reason to edit the question editing them just for "bumps" is a Bad Thing, but if they can be improved by all means improve them!)
- Unanswered questions will sometimes be "bumped" by the community user automatically.
That's designed so a question with no upvoted or accepted answers will eventually find its way back to the front page and hopefully get an answer.