Debian updates its stable release repositories every two years (aside from pure bugfixes and the like, of course) because this is what it takes to have a rock-solid software release-- with a truly negligible amount of issues for the computer-naïve "average user" to be bitten by-- given the resources they have at present and the overall state of upstream software. If people want more frequent updates, coupled with the same overall reliability that Debian has always been known for (far more than many other Linux distributions), they're welcome to contribute.