The All Purpose antennas are designed to be used in a variety of situations. This applies both to the electrical properties and the mechanical properties of the antenna.
For example, the A146-5EY 2-Meter Yagi's radiation pattern is a compromise between the high gains possible with other yagis and omnidirectional verticals. It has some gain, but still a fairly wide beam-width (especially in vertical polarization) in order to minimize the need to rotate the antenna. Mechanically, the antenna is designed to be physically smaller than high-gain yagis, extremely easy to assemble, and durable. This means it can be hung in a tree or erected on a mast for field use, or taken up un-assembled into the attic and easily assembled in tight spaces. This also mean the antenna packs and travels very well, making it a great "go-bag" antenna for emergency uses.