There's no hard evidence for this, but we know that this was a science mission first. Get the big hunkin' mirror into cold space. It was already extraorbitantly expensive.

No budget to try wildly new things. (The folding was already new enough.)

Also the constant scolding by Congress about the budget overrun has the very predictable outcome of fucking up the overall efficiency of the project. It got assessed and reassessed and committee oversighted, and costcutted...

but of course there was nothing to cut, and everyone knew. It was already risky as fuck and debating how much the sunk cost fallacy applied basically became a pastime.