Any application needs time to be used and tested enough time in order to make it stable. One of the greatest goals of Debian is stability. It's released when it's ready and applications included in the repositories have enough time to be tested through.
2. Debian offers stable, old stable, testing, *and* sid
Why should this be an advantage? First, because there is a stable release, which will fit both desktops and servers. Since Debian stable releases happen rarely, software can get a little old. So any can get to choose 'testing', which is tagged that way because applications are tested more but they are still usable. Sid is bleeding edge, which means applications get in usually as soon as they are released, so you get the newest software only by installing a testing weekly snapshot and upgrading. Considering the stable and old stable offer software which has been tested and stripped for critical bugs, testing usually proves to be the perfect alternative for a user who wants to use up-to-date tools and applications, which include the latest features.