A couple of ways this shows up: 1. making your system rugged to handle extreme weather. These sites need to last 30-40 years without breaking, which pushes you to use pretty heavy + large components. Piles get driven several feet into the ground, so even with unfolding systems you're still probably pile driving. 2. tracking -- adding the complexity to enable rows to rotate to face the sun makes it harder to make the system portable. Basically all large-scale solar getting built is single-axis tracked. 3. module cleaning -- it's important that vehicles can traverse rows to clean dirt off of modules on a regular basis. Having structure that connects the rows together may make this more difficult.

None of these are intractable on their own but together they make the approach you describe very difficult.