This is oddly personal but for me its kinda' pure greed born from the realisation i want to see new worlds and new experiences plus the fact i get really bored fast.
With my family and worklife and cost I don't get the chance to experience new worlds and i want to see the world. And building PC's means i can experience that through forms of gaming. Some obvious choices (GTA, Detroit, motoracing - but other silly ones as well born about by my general love of gaming as a skill).
Its pretty sad, virtual, and disconnected from reality - but in other respects is amazing. I'm a slave to videogame experiences. I'm into photography and music and creation too (so my PC helps there) but i'm restricted in where i can go or what i can do. I do lead a fairly normal life i suppose, but a LOT of that life is PC based.