I would personally advise against that, but HELCs are a popular financial vehicle in order to do exactly that.

Yes, the economy of the entire industrialized world runs on this.

People borrow money against their house to buy a car or a boat because rates are much better. The bank tells them to borrow a few ten thousands extra while they are at it, since the rate is so good. Why don't you take a vacation or get that new thing you wanted to buy?

From where do you think everybody has so much money to spend, while you are working full time and have nothing? It's not only credit cards...