Staying low
A low stance lowers the center of gravity while bending the knees. Both of these allow for quicker movements as well as added power. This is important, especially at higher levels where quick footwork and power dominate. At the beginning stage it's not as comfortable, but once you get used to it it's hard to imagine playing without a low stance. So it's a good idea to get in the habit early in your playing career. (If someone plays most of their life but are not professionals, like 99.9999% of us, is it a "playing career"?)
Many players say they can read spin better when they stay low, especially when returning serves. Many players adopt an extra low stance for receiving serve, and then go to a less low stance the rest of the rally. I've always suspected that the low stance doesn't really help read the spin better so much as it allows them to react to the spin faster.
When players think about footwork, they mostly think about moving to the ball in a rally, where they move mostly side to side as they run down each shot. Footwork for returning serves is way underestimated, which is one reason players often return serves awkwardly as they reach for balls they should move to. In that split second as the ball leaves the opponent's racket a receiver has to make a snap decision on whether to step under the table and move in to the forehand, backhand, or middle for a short ball; whether to step off from the table if the ball is extra deep; whether to move to the wide forehand or backhand for a deep serve there; whether to move left or right to receive a deep ball to the middle with the forehand or backhand; whether to use a forehand from the backhand or (mostly against short balls) a backhand from the forehand side. A low stance that gives a quick start makes this a lot easier.
U.S. Nationwide Club Team League