How do we know that they haven't already been doing this?
No but seriously, this would give people something to do if they get bored (which is HIGHLY unlikely) and be exciting to try and find.
This could also be made into an event, whereby the first person to find a hidden tomb/temple would be rewarded with treasure (5 mil or something like that).
AFAIK, they are doing this already.
Check out the Abandoned cop car South of LV.
It gives these drops randomly -
1. U found a handcuff without key. You throw it away.
2. You just found $10,000 worth of drug money seized by cops.
3. You found a used body-bag. You've been infected with Chyladimia
4. You found a cop radio. You can now listen to cop's conversations using /radon.
5. You found a MP5 with 500 rounds.