Humans tend to shine ridiculously bright spotlights into the sky. Imagine an alien vessel going past and being blinded by these lights. -- Anon Guest
[AN: Most of our lights don't work like that. They're dissipated by the atmosphere and disperse as they go further from the source. By the time you're at cruising altitude for airplanes, they're invisible to even the most perceptive of observers. That said, we're busy inventing some pretty gnarly lights...]
Humans like to prove things are possible. Even when the principles behind engineering the proof are patently ridiculous [See linked file: Mythbusters]. Therefore, they repeatedly attempted methods of contacting alien life that were repeated and undeniably proven ineffective. That would never stop a group of Humans for trying harder.
"So these are an array of argon lasers, grouped into a mirror box, aimed into the sky at Moonbase Armstrong. We have observers all through Armstrong, looking for us. It's a clear night. We have approval to do this in three... two... one." A knife switch is thrown. Equipment makes a subtle thrum. A countdown timer begins...
A tourist vessel, ignoring the posted warnings, loses control and almost crash lands in the small field in Roswell, New Mexico. An angry passenger exits. "What the flakk are you Humans playing at?"