Thank you Ketama,Ark and meraj !

Actually I was asking about the thing that Meraj mentioned.

There should be any law or rule when USCIS sends H1B approval without I-94. 
In which case they send without I-94 and we need stamping ? 
Like Meraj mentioned " gab between job, or if you work for desi craps"..or anything else ?

Is this just random or some rule is there ?

Thanks in advance