Walkthroughs of standard maps, focusing on SPEED.

The reason for this phenomenon is well-known: random numbers in a computer are actually pseudo-random! Only a "white noise" generator can produce truly random numbers. You can read more about it, for example, here.
Personally, I have no complaints about the game in this regard: it is not obliged to provide you with the desired artifacts/spells/heroes/skills, etc. on demand! The player must be able to make the most of what they get - otherwise, their ability to play is worthless!