Of course that's the only reason and we all know it. It's fine. If no town payed for a start we'd be probably left without the Giro d'Italia.I think the real reason this stage happened was because it was the only reasonable bid for the stage start and they thought they could get away with one.
I just don't think the organizers had any major plan in mind when designing it, like testing endurance or hoping someone would bonk tomorrow after today's effort. Because it was pretty clear to anybody that today would have been a no effort for a pro peloton even if the stage was ridden in its entirety.
Sure, they should have thought about it months ago, when the whole route was presented, but I've long given up on the CPA or any cycling association to actually do anything sensible these days.