Question: Why do you think the CRAP Principles are important in design?
Answer: I've studied the CRAP principles in several classes now and I think that the reason that they are important in design is because, very simply, they present a method of design that is easy for the the average user to access. Provided that the user is not color blind, or is simply unable to see the content of your page, the CRAP principles seem to resonate with the naturally occurring brain patterns in people.
People can see your material best when there is some sort of contrast between the various elements on the page. Without contrast, you end up with text or images that blend into their surroundings, requiring the viewer to strain their eyes to try to obtain the meaning from them.
When you repeat elements, it helps provide continuity for the viewer. For example, if you repeat the same font and size of text when you create a new section head, the viewer will quickly recognize the section heads for what they are. Similarly, regular text is easily spotted when compared with the rest of the page and indented text might be quotations. As long as the same format is used for every occurrence of a specific element, the viewer will not become confused.
Alignment is good because it keeps your material from looking scattered. Unless you want a scattered presentation for some reason, using alignment only makes sense is another tool that helps you organize the various elements you are using.