Sure, it can become an addiction, but it's a hobby and there is some pleasure than can be obtained from the next acquisition.
Once one get's past a SAK, a multi-tool, a SD/tactical folder, a "user" folder and a couple of fixed blades (bush craft and chopper/lopper/wood processor) "need" becomes less of a driver in the analysis.
It's a hobby and, like all hobbies, it's purpose is to pass time (many money) pleasurably. Some go to customs for their fix, others exploit to the maximum a particular brand, maker or style - others each and every iteration of a specific model. We all do what we do in different ways. Me? I've got utilitarian users that will last me and my progeny lifetimes ... Beckers, Cold Steel Voyagers and the like; yet, notwithstanding their durability I have back-ups and, for my favorites or discontinued models, back-ups for the back-ups! Other than my plethora of Beckers, Emersons and gaggle of voyagers, my time in the Keys, Bahamas or up/down the Atlantic coast in and around salt I've grown passionate about Syderco's H1 "Salt Series" line-up and have multiples of them as well and, yes, a few back-ups - though, truth be told, before I got into H1, most stainless steels have served me very well over the years with simple care.
I enjoy owning my Sebenzas, One-Piece Range CRK knives, Busses - they're all great but I'm hardly ever out of the house without an Emerson (have way too many of them too), but my users and beaters is where my collection has wandered and those darned Beckers seem to rub together in storage and multiply.
So, if a SAK, a multi-tool, a SD/tactical folder, a "user" folder and a couple of fixed blades would satisfy my (and most's) "needs" ... what keeps us going?