well i'm not too sure too but say if.....ok,say if you're the ET.and if you've found some other unknown living race in some other planet whose really really primitively stupid and wish to teach them at least a few basic things for the real deal.now would you teach them straight away the techs of planes,floating crafts, other super-advanced theories etc...??
i dunno about you (maybe you're very kind

),but if i were you or the ET,i would rather go for just the basics to start off.i wouldn't wanna give all my stuff to them,the least maybe i could exchange for some fortune right?what if 'these' primitive people took our teachings, get really used to it, progress quickly with it and backstabbed our ET race due to the massive super modern tech that they've achieved in just such a short period?would that make them feel superior,powerful or even like a God and return our favor with an extinction to our race?we really don't know much about them,or thier real personality....so why would i give them every one of my techs??right?wouldn't it be wiser if i would....do some checking on them first before i throw in my goods and create a bond with them?
we certainly could see here on Earth i mean let's face it,there are millions of these 'backstabbers' living in this world and from that we've to be cautious when dealing with this people.so if you would imply this theory into the ET-human thing.....why not right?
they've not known how quick is our progress in technology so they've decided to just give us the simplest of technology (eg pyramids) and then experiment how far do we make our progress in this.who knows,maybe if the ET people never did shared thier knowledge,we could still be leaving in caves??
and that could be shown in nowadays sightings.remember the ufo-concorde sighting?that's just one of them to show you that they're still observing us and probably waiting for the right time before they could befriend us.
what do you guys think of this?i maybe crapping but my thoughts are strongly based on this.