I think that nowadays a lot of empty threats are made and there are no real consequences for children.
I was terrified of my mum as a kid (I'm coming up 50), she was very free with her hands and what she said went, no argument you did as you were told or the consequences were physical punishment along with a lot of terrifying shouting from her.
I vowed to be different with my children. As it happens I have just the one. When he was small I used time out as an appropriate method of punishment, he got 3 warnings and then a time out. I told him "no" a lot! I think the most important lesson I learned was to be consistent with him. Also he got whatever I said he would, be that an ice cream for good behaviour or an early bed time for bad! He's got a fiery temper and has at times been difficult, but I think having the expectation that he would behave in a certain way and modeling that for him had really helped.
I cannot get my head round people being frightened of saying no(sometimes repeatedly) to their children, I know of someone who was prepared to change an expensive piece of equipment to one their child couldn't mess with rather than just repeatedly saying no and removing their child from the situation every time they are where they shouldn't have been. It takes patience and perseverance but it works in the end but it is hard work and I guess not the easy option.
I think that is probably part of the reason, raising a child is not all unicorns and rainbows it is a lot of hardwork, a lot of saying no, being consistent and following through. When people are working hard and running homes and everything else they have to do, sometimes it's too hard to stand in front of a tantrumming child and say no, it's much easier to give in for an easy life. The natural consequence of that, even if it initially comes from a place of love, is that the child had no real boundaries, and a sense of entitlement, which is not great for anyone else.