Hi DRAZ, welcome to ASC.
Everyone has essentially touched on why we look to more expensive, real deal parts and gear. You have to appreciate that half of airsoft is a fashion show, so if you've got the latest in high speed gear and accessories you'll be ahead of the game. Not that you're in competition with anyone, but people like admiring unique and cool stuff and let's face it, we like showing it off too (ie. your list of guns
Another comparison would be, why would you bother buying a SIG P220 when you could buy a Ruger P90, or a Wilson CQB versus an Imbel or Firestar? That might put it in better perspective for you. A lot of us own real guns too, heck my gun collection was at one time valued at more than anything else I owned (low five figures). My interests shifted, I sold most of my good stuff, and discovered airsoft. I have a couple of regrets but for the most part I'm enjoying the sport
of airsoft as a whole a lot more than real shooting. It's a LOT cheaper on ammo, more dynamic and intense, and very diverse. And I've shot IDPA, IPSC, PPC, F-class, and other disciplines. I enjoyed them all but airsoft just offers that one extra factor of "combat" (and I use the term loosely) that none of the others can really touch.