Personally, I do not think that is's only a cultural thing, but also a personal opinion. I live in Germany, and for me, too, those popups are annoying. I know how to fill a damn form online most of the time. However, I also know people, who do not want to do stuff like that. They want someone else to explain everything to them, make a simplified suggestion and then pay money. They are German, too, but they have a different opinion.
For a company, it is difficult to decide whether you want the additional help or not. So they will usually just go ahead and try to make things simple for you, ideally promoting a product which maximizes their wins while keeping you in a good mood, so you keep buying. Go to Amazon, take a look at different products. Amazon will offer you a "Amazon's Choice" product, which is usually not the cheapest or best product. And even when taking a look at a product, Amazon will always promote products which are sent from their warehouse, even though another seller has a cheaper price. It's their way of "choosing for you and making your life easier that way", but which also is the biggest benefit for them (not you). Most of the time, that strategy will work, and you might not even notice what just happened.
Now, what I think you mean by an annoying website, is when this concept goes wrong. A company overdoes its "help" or does it in a wrong way, which leads to a rather bad user experience. Imho, it's not a problem of the concept, but rather an error on the company's side. As such, I think it is fair to avoid making business with that company or even write negative PR, based on your experience.
So, what should you do if you have to decide if and how to support or pamper a user? Basically, it boils down to planning and creating good UX. Helping your user is always a good idea, but if I had to do it, I would try to stick to passive elements, which creep into the the application, for example by making decisions for the user without them even realizing it. Additionally, I would, if possible, add very a very simple way to actually get support from a human - for example a button, which you can click in order to initiate a pop-up text chat. A user should not have to decide every little thing, they should not have to decide everything at once, and they should feel that they are not alone.
Good UX is difficult.