They don't give a thought about how they will climb the next one or that they will not have permanently improved themselves in the process. Life is more about the journey than some end. Say you get to the top of the mountain via your miraculous means, it would be like getting to somewhere you feel out of place. You didn't climb your way there; you lost the opportunity and motivation to acquire the skills. And then what if you slip on the mountain? For someone who climbed his way there, it will be piece of cake task to get back up and regain lost ground. But for someone who was dropped off at the summit, that will be a major disaster.
The trouble with dreams that are set up like castles in the air is that they are not fulfilled (and if at all they come true, the owner needs as much the miracle that made it happen to keep it). And most importantly, the biggest dreams were not achieved that way.
Real castles aren't built in the air. Disneyland was built from ground up and not top down. Dreams are meant to be built and not made to suddenly appear. Walt Disney worked his butt off to create Disney and the foundation of the amazing things we are now used to seeing Disney create. Every enduring dream is built from hardwork and foresight. Not just desire.
Whenever you see someone all full of talk of big things and no action made towards achieving his goals, you should help him with practical steps he can start taking now.