look it up on Google?
http://cdn2.ioffer.com/img/item/577/348/71/o_GAqywyKYJFmkFFO.jpg
Well yeah, Google doesn't offer much in the way of a dialogue though. Still, I took the advice, and determined that much of the ultra-gaudy leviathan that is the modern strip was built in the seventies and later (changes in the gambling laws meaning competition from Atlantic City was the catalyst, apparently.)
Also found this pic:
http://www.inoldlasvegas.com/downtown/1950s_FIFTIES_VEGAS_COLOR_PHOTO.jpg
Which is vey, very New Vegas I think. So no tricks missed after all.
No, They just did'nt want to get sued.
Why would they get sued? Who would sue them? Did Bethesda get sued for using the Capitol Building and the Lincoln Memorial? San Andreas had a version of the Vegas strip in it iirc, don't remember Rockstar being sued as a result.