A basketball court requires long straight and square lines. Making sure that the key is square requires tools and techniques not in every home. either geometry or and laser square which not everybody can do. It is really easy to make a mistake and small errors are very noticeable. For example using a string and chalk to make a circle works great. We all did that as kids But with a 20 ft piece of string, we found that that string stretch makes it difficult to use this technique on a basketball court.
Unlike a tennis court, the basketball court has straight lines, curved lines, and blocks all at precise dimensions. It is complicated and can take a while to measure and paint.
The size of the court is so large that a small not noticeable error in one spot becomes glaring at the end. Repainting is not an option.