What happens when this thing breaks? Will they abandon a $10B device in space? Or maybe send a guy to go out to L1 and "turn it off and back on again"? Lol
It's too far away for humans; nothing on it is designed as an attachment point; and body heat on the parts on the dark side of the sun shield, let alone engine exhaust, would risk further damage.
A robot might be able to fix something, but that risks being more expensive than building another telescope — I don't know how much of the cost was designing it vs. building it, but a second would probably be cheaper than the first.
I would be curious to know why they didn't implemented anything like this. I know that no robot, space vehicle or any other technology currently exists that could repair such a spacecraft in L2, but I would like to know whether leaving this door open by adding one or more attachment points would have increased the cost of the telescope too much.