In the days when laptops were generally larger, more often made of plastic, and frequently carried in whatever briefcase or shoulder bag they would fit in, many of us, myself included, used a padded sleeve as an extra layer of protection.
In recent times, more laptops are built from sturdy materials such as aluminum and carbon fiber, and often with very sturdy single-piece construction for their bases. There are also a surfeit of slightly padded laptop bags and cases of every size, many of which are stylish enough for everyday use without looking like you're on your way to a corporate meeting.
There may, however, still be times when you want a dedicated laptop sleeve. If you find yourself in that situation, and you happen to have a 13-inch MacBook Air or MacBook Pro, accessory and case-maker Pad & Quill has a high-end version to go with your high-end laptop.
The Pad & Quill Sleeve for MacBook is a $99 leather-and-canvas cover for your MacBook (the 11-inch version is $89), that should also fit similarly thin ultrabook-style laptops such as the Toshiba Kirabook or Dell XPS 13.