If there's a lot of demand for rollercoaster rides, the rollercoaster will not stop operating; instead the queue of people in front of it will increase.
It's not like a bridge or elevator where we have a certain number of people that can use it, and if one more person joins, the whole structure breaks apart and everybody perishes.
Those guys are running a website that provides an interface for some specific hardware. Just like file hosting providers back in the day selling their terabyte-sized hard disks in 100MB-increments.