In singles, you can serve to all parts of the table. This means you can usually force your opponent to receive from his weaker side, whether it's forehand or backhand. Not so in doubles! Now your opponent can choose his stronger side to receive. If you serve long, he'll probably attack it, usually by looping. If you serve short sidespin or topspin, he'll probably attack it as well with a flip. If you serve backspin, he can drop it short, push heavy, or flip it to a corner. What is a server to do?
Surprisingly, the answer is often a very shot, very low no-spin serve. At the world-class level, it's the most common serve in doubles, and often in singles. Why is this? A short no-spin serve is tricky to push - it's easy to pop up, and you can't put as much backspin on it, since you don't have a ball's spin to rebound off your racket - you have to create all your own spin. It's also not as easy to flip aggressively as a ball with spin since you can't use the spin of an incoming ball to help your flip. A topspin or sidespin ball rebounds out with topspin when struck properly. A backspin ball can be aggressively flipped, and the backspin continues, except now as topspin. (Often the receiver can put great topspin on this ball, especially with a backhand banana flip.) But a no-spin ball doesn't rebound out, and you can't use its non-existent spin. Plus, it's easy to keep a no-spin ball low. (A slightly high no-spin ball is easy to attack, so beware.) This doesn't mean you should serve all no-spin. But it can be the primary serve, with other serves used as variations, especially short, heavy backspin.