The point is not to simply make extra work. It is to make a better site. For E-Commerce sites the extra time spent on layout and font choices can easily mean an increase in sales. The extra columns do give you the ability to add more useful content to a page. Lets think about page of an E-Commerce site. For smaller browser windows you only want the most important things above the fold. (in the window) When you have more columns you can add things like panels for testimonials, featured products, top sellers, sale items, promotions, shopping cart summaries, similar items, upsell items, other people who purchased this also purchased the following, product reviews, it goes on and on. Would I do the multiple layout option on a simple site or a blog etc.? Not likely.

Overly complicated is a matter of perspective. To me it is less complicated because to make a fluid design look really good in a wide range of sizes requires quite a bit of tweaking. Then you end up with that email saying I can't click on such and such because the link is covered up by something else. Because you never thought to narrow down the browser window to 400px or less as a test. You may end up between a rock and a hard place if the fluid layout is unable to resolve certain issues correctly.

You are not "hiding columns of random information". You are prechoosing what is important in each layout.
You are making it sound haphazard when the whole point is to have 100% control yet be flexible.

A better simplification is this.
1) Give the visitor several predefined, pretested choices of font size.
2) Allow the visitor to choose between several different layouts with different numbers of columns. The idea being give flexibility but with predefined, pretested choices only.