Also, it is rare for a random number generator to be truly random. Some of them are random for some purposes, but exhibit patterns when used for others. I think what people don't want is a random arrangement of (let's say) bad guys on the screen that looks great under Windows but tends to have a less random appearance under OS X, for example.
To elaborate here, some random number generators pass test for randomness for long sequences, but not short sequences. So your "random" placement of enemies commonly ends up with visible clumps.
To elaborate here, some random number generators pass test for randomness for long sequences, but not short sequences. So your "random" placement of enemies commonly ends up with visible clumps.