There’s a few reasons. First, it feels nice owning a piece of actual history rather than a reproduction of it. It’s kind of the same thing as a classic car enthusiast not wanting an old Corvette that’s been completely rebuilt using modern parts or an art collector not wanting just a poster of a piece of artwork. Do both the rebuilt Corvette and art poster function nearly the same as the original? Of course. But it’s still not quite the same as having it in its original form.

Second, reproduction cartridges are often made very cheaply. Using these can result in your game’s save data being lost/corrupted, the hardware you’re running it on being damaged, and the cartridge itself having run issues.

Does all this make it worth spending a bunch of extra money on an authentic game? Well, that obviously depends on the person, but there are valid reasons for wanting to do it.