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.
This is a narrow view of what makes the Souls series appealing and I happen to disagree with it.
In my opinion the point of these games is not "get souls, buy more shit." The point of these games (along with the difficulty) is that you can play through them in any way you please.
Want to turn the game into Borderlands: Fantasy Edition and co-op every single level with no less than three summons (sloppy netcode permitting)? Do it.
Want to RP as Rocky and exclusively punch your opponents? Do it.
Want to avoid leveling entirely and wear no armor? Do it.
The desire to do things like challenge runs is, quite likely, far more popular than you probably think.
I strongly disagree with this. Both Demon's and Dark Souls SL1 classes are set up perfectly to be able to beat the game at that level. It's definitely intended. Pyromancy with no stat investment, elemental weapon upgrades, the occult club and blacksmith hammer that can be used at SL1... it's all intentional. The ability to troll new players is also intentional as well.
Exactly.
From Soft knows their audience. They built these games with things like challenge runs and sequence breaking in mind (seriously, that's the whole point of the Master Key). Obviously not their primary design goals, but they sure as hell wanted players to have the ability to do those sorts of things.
Toddhunter already brought it up, but yeah, invasions were never meant to be perfectly balanced, skill-based encounters. You want a fair duel, use the Red Sign Soapstone.