That's only even possible for most SL1 players (those who aren't super-duper hardcore) because of the tons of non-scaling damage types. If From had put level requirements or hadn't put non-scaling weapons, very few would have done the SL1 run (it's still possible as you see people do "no upgrades" runs anyway), and no one would have missed it or lamented it... because guess what, the point of the game is to explore for treasure to help you vanquish your foes, and spend the souls you earn on things that help you progress (weapon or armour upgrades, buying spells or rings, leveling up etc). Also part of the tension of the game is the fear of losing all those precious souls. SL1/no-upgrade runs are quirky challenges a very tiny minority of people do to gimp themselves and make the game more challenging to them, but it has nothing to do with how the game was conceived.
I'm not even talking about ganking, but I disagree. I'd rather have fun and balanced PvP and low-level invasions than allowing a minority of nerds the "freedom" to beat the game with a level 1 pyromancer with an ascended+5 pyro flame and a lightning+5 hand axe. And hell you'd still have freedom to try to beat the game using any kind of "challenge rules" you'd want: you can still try to beat the game at SL1, only you'd be much weaker. Isn't that what SL1 runs are about anyway, the challenge?