You get an awful lot of loot in Guild Wars 2, and most of it usually falls into one of two categories: useless, underpowered stuff — “greens and blues” — that clog up your inventory and are salvaged en masse for crafting materials; and bags that contain bags that contain bags that contain bags that contain that useless, underpowered stuff.
On the bright side, since bags typically stack, that second option can take up less space. Bags of Unidentified Gear were introduced in the Path of Fire expansion, replacing most gear found in zones related to that expansion, and making it easier to sort and dispose of the vast majority of loot drops. In the patch coming March 26, that convenience will be extended to Core Tyria and Heart of Thorns zones, as well.
The changes are detailed on the forums, and they include a change to how Magic Find works on such items. Notably, your MF will only take effect when you obtain the Unidentified Gear, not when you open it. Previously, it affected both rolls, thus doubling its utility. As stated at the end of the post, “Overall, you’ll get the same amount of loot and won’t have to play inventory wars as much.” It’s nice to see that even the developers are in on the joke.