According to The Hitchhiker's Guide to the Galaxy, "A towel is about the most massively useful thing an interstellar hitchhiker can have." The link above gives some of the many ways a towel helps, such as (I'm not making these up!) "use it to sail a miniraft down the slow heavy River Moth; wet it for use in hand-to-hand-combat; wrap it round your head to ward off noxious fumes or avoid the gaze of the Ravenous Bugblatter Beast of Traal (such a mind-boggingly stupid animal, it assumes that if you can't see it, it can't see you)" and so on. But amazingly, Douglas Adams left out the value of towels in table tennis.
Let's start with the obvious: you use a towel to wipe sweat away and to wipe your paddle and the ball off. (If it's humid and you sweat a lot, ideally have two towels, one for you, one for your paddle and the ball.) But there's another huge reason to have a towel in table tennis, and it's not so "You can wrap it around you for warmth as you bound across the cold moons of Jaglan Beta."
The other reason for a towel is so you can towel off every six points. You might way, "Why do I need to towel off if I'm not sweating?" Putting aside the question of why you aren't sweating (you should if you are playing the Olympic Sport of Table Tennis), there's a more practical reason. It gives you an ongoing habit that allows you to take a mental break, clear your mind, and focus. If you do this regularly, it becomes part of your routine, and really helps the mental aspect of your game in a Pavlovian way. Your subconscious is no different than a dog's in this. (Besides coaching table tennis, I'm a writer, and I also use Pavlovian techniques - after many years of doing so, all I have to do is drink a Dr Pepper and I go into writing mode.) When I coach players, I'm always harping on making towel breaks a habit.
The game is more mental than physical and taking that towel break is an important mental weapon. Take it!