Time spent alone
Whether it's been an unusually hectic day or you just don't want to listen to your son's Rock Band® game, isolating the master bedroom away from other bedrooms in your home has a significant impact on it becoming your own private retreat to relax in and rejuvenate. That's why you're seeing more designs with the master bedroom on the main floor and secondary bedrooms either upstairs or in the basement.
If you have a 1-story home with all the bedrooms on the main level, look for home plans designed with other areas doubling as noise buffers from the secondary bedrooms. It's easy to see when the master suite is on one side of the home and secondary bedrooms on the other. But even when all the bedrooms are on the same side, the placement of closets, bathrooms and other spaces can help seclude the master bedroom and offer the privacy you're looking for.