<human>: Can you give me the gist of the text in a nutshell?

In work at the moment people are spouting a load of nonsense about stuff they've have seen online (slow to catch up I know) about extraterrestrials helping ancient people build mundane objects. 
My question is why do people believe in things like this?  Is this just a modern belief system evolving from people shifting away from religion and things like this?

The Nazca lines for example have been proven to occur naturally and from this observation it is likely old civilisations misinterpreted this and copied some symbols for themselves?? Is it so hard to believe that ancient civilisations built pictures for "their God's"?  A theory lies that they were used for landing locations and landing strips etc. but lets face it, inter stellar travellers need poorly drawn shapes to land their SPACE SHIPS.  I would have thought they would have used computers myself....

Crop circles are the big one... the two people responsible for the first crop circles openly came out and admitted it was them and reproduced the results for the skeptics... yet people still believe that aliens caused them???
<bot>: Are aliens a replacement for religion in peoples "I can't explain this" mentality?  Why are people stupid enough to spend money reading about it.