As an interested bystander I've never quite understood the purpose of ramps for takeoffs. It would seem to be an (inevitably less than 100% efficient) way of obtaining vertical speed at the cost of forward speed.
Given that the thing will fly regardless if it's going forward quickly enough, why is this tradeoff worthwhile? Is it some sort of special voodoo relevant only to aircraft with some sort of vertical lift system like Harrier or F35B?