When I started out in the systems administration and hacking worlds a couple of decades ago - and even when I first moved into information security as a profession nearly 15 years ago - the dominant incentive was the ego trip: what can I get away with? Truth be told, that's the original (and to many, myself included, the "real") meaning of hacking: to take something and make it do what I want, rather than necessarily what the creator intended. A hacker is someone who is highly interested in a subject (often technology), and pushes the boundaries of their chosen field.
That culture has nothing to do with malicious use of computers - nay nothing to do with malice at all. It is all about solving puzzles: "here's an interesting <insert favorite item>; now what can I do with it?" The hacking ethos brought about automotive performance shops and the motorcycle customization industry glamorized by West Coast Choppers for two examples. A hacker could be known less controversially as a Maker, or a tinkerer, or a modder - or an engineer.
Hacking in its purest form is perfectly legitimate. If I own a computer, or a phone, or a network router, or a TV, or a printer, or a programmable thermostat, or an Internet-connected toy, or a vehicle, or (the list could go on forever), I have every right to explore its capabilities and flaws. Within reasonable limits (various transportation authorities may have something to say if I add flashing red and blue lights to my car and start driving down the highway), it is mine to do with as I please. Where it becomes ethically and legally questionable is when I stop tinkering with things I own, and begin tinkering with something you own, without your permission.