Ridiculousness in RPG #1

One thing I love about rpg's, especially early rpg's, is the ridiculousness of many of the creations.  Look through lists of early monsters and magic items, and you'll find all sorts of good fun.  Some of it is at least kind of logical, while others, well, not so much.

Case in point number one, the Brain Mole.  I never really did get much the place or point of this little guy:

Yeah, this little guy...I mean, he's like, a mole in all respects, other than the fact that he can basically eat your brain if you are any kind of psionics-based character, not that that's a bad thing.   So, anyway, unless you're in the rare percentile of characters that actually HAS psionics in AD&D, a chance that in itself is ridiculous, mathematically, you don't need to worry about this little critter any more than you might a goblin or kobold child, which, in my honest opinion, is dumb.  

And that's the one major issue I have with "early" D and D, the "randomness of the universe" nature to things as presented in the guide/rule books.  I mean, here we have a totally randomized "monster" that can only really be truly dangerous to what would actually be about 1-5% of all player characters, assuming the rules for psionics were handled correctly (again, an issue for a later date).  So, what's the point?  Why  include this little guy at all?  Honestly, I can't say.  Maybe you all have a better idea of things than me...