My own excuse is the lack of clear sky requiring a raised observing platform. So far, so good. Now I am up there, I demand some creature comforts. I want my instant gratification, or else. So I don't want to be getting lots of things out of waterproof bags or boxes before I can "get going." Protective shelter is essential for all the kit to function from switch on.
These demands have been fulfilled in only a very limited number of geometric/material forms over time. Mostly in the way of hemispherical domes. Minimum volume with minimum material consumption in its construction must be weighed against the greater difficulty and/or cost of 3D construction. A dome is traditional and suggests some seriousness is being applied to the hobby. Though not exclusively and I mean absolutely no disrespect. Other shapes are certainly possible and some very expert imagers work "naked" out in their gardens. Or even on their drives, patios, terraces, lawns or decks.