Getting ready to move from Okinawa to Mainland Japan in just a couple more days. Took a car of mine down to one of the local ports for shipment to the mainland.
While there I saw a multitude of heavy mobile equipment such as cranes and several of them had folding bikes folded up and stored on them.
I'm going to surmise that once they set up to lift they're probably a ways away from a toilet, convenience store, lunch, vending machine, etc. and they use the folding bike for just such circumstances.
Anyway no great revelation, I'd just never considered folding bike usage in a construction type setting but it makes perfect sense.