Traditionally, decks are built in squares and rectangles for simplicity and cost savings. More elaborate deck designs will introduce angles or bayed areas to add some visual interest and usability.
Wood can be a tough material to work with when it comes to curves and because most decks are wood, builders have generally avoided curved wood decks and gone with the angled look. It makes sense.
Now that manmade composite and PVC materials have become so prevalent in the industry, it has become easier to introduce curves or a radius into deck designs. These materials are easier to bend and curve than wood. That's not to say it's easy-because it's not for the faint of heart, but it's not as tough as wood.
The geometry of incorporating curves and radii into a deck project can be complicated. A fair amount of serious math is involved to make everything work our properly. Transferring the concept of the radius on paper to a completed deck is not the simplest thing a deck builder can do so many builders just don't offer curves as an option.
Peachtree Decks and Porches has done hundreds of curved decks over the years so they have become not too big of a deal for us to build into our projects and don't increase the cost all that much. Curves add a practical design flair that turn an average deck into a "wow" deck.