Because I read about it (I asume you mean permaculture), tried it out - and dismissed most of it.
Permaculture is indeed great as a concept, but is in no way as easy as people tell you it is. Most of what people tell you about is close to scam (even if it is wishfull thinking)
Are you telling me, that you don't have to do weeding, like OP said, at all?
So not in the protected greenhouse, but out in the open gardens, where there are seeds coming from everywhere?
The dirt will get covered in plants, but you don't have to pull up everything you didn't plant yourself.
What about them? A weed is simply an unwanted plant. If they do no harm, why do you want to spend time removing them? Again, plant a good cover crop and don't weed. Your soil will be better, you will use less water, and there's no downside.
>(and snails)
Nothing about permaculture says you can't deal with snails. You can still deal with snails/slugs however you like. The obvious being simple copper wire or beer traps.
>Are you telling me, that you don't have to do weeding, like OP said, at all?
Correct. The only plants I pull out of the ground are root vegetables.
>So not in the protected greenhouse, but out in the open gardens, where there are seeds coming from everywhere?
Yes. Again, seeds coming from everywhere doesn't matter, because a dandelion in your potatoes doesn't hurt anything.
In a small backyard garden you might need to pull out a couple dozen weeds over the entire growing season.
You'll also be able to reduce your water use significantly because you've eliminated most of the open/broken soil that loses water to evaporation.
And I do use permaculture principles in my garden, but if someone tells me, no weeding is ever needed - then they either do gardening on a different planet, or are just lying.