This is not so when you only buy the license to use a product (software is another example of the same thing). When you buy MS's Office software then you don't own the software. You have bought only the license to use it.
And yes, does MS ever restrict usage....
Just don't buy any patterns sold with such restrictions. There are a gazillion ways to put commonly used quilting elements together your way (the only right way).
The emphasis is on "commonly used" and "commonly available".
You can't have (and won't get) copyrights on commonly available patterns. Period. For a design to be protected it must be NEW AND UNIQUE.
The 'day and night pattern' on the quilters cache site for example is neither new nor unique. Don't worry about using it the way you see fit.
Why would anybody pay good money for patterns (or the license to use a pattern for personal use only) that your own head can produce for you by the dozens in an hour?