In my experience this isn't true at all.
Hand techniques in Taekwon-Do out number foot techniques. In the ITF you can use any hand technique in competitive sparring, as long as it's covered by the hand gear (so knife-hands are fine, but you couldn't use, for example, an elbow since it's not covered by protective equipment). You will often see ITF competitors use a mix of hand and foot techniques, as well as rely on hand techniques once they have closed in range to good effect.
Hand techniques are also widely used in pre-arranged sparring (3-, 2-, and 1-step sparring), semi-free sparring, free sparring, and self-defense. For pre-arranged sparring you may use any hand technique, not just the stereotypical punch from a walking stance. Self-defense is often done against not just a wrist grab but an attack using a wide variety of attacks.
The reason why people think Taekwon-Do neglects hand techniques is because the WTF has spent about 40+ years or so promulgating a sparring rule set that does neglect hand techniques and they (and the KKW) are the most visible Taekwon-Do organization out there. People have recently said that with the advent of electronic hogu punches are now scored more often (when I trained at a WTF/KKW club in college the instructor was an International Referee for the WTF and told us that he had seen a total of 6 punches score in international competition after many years of experience so really they had no where to go but up). But the rules still only allow punches with the fore fist, as far as I am aware so even with the increase in punches scored you're still going to get a much lower number of hand techniques allowed.
The WTF will continue to use their rule set and so people will continue to view Taekwon-Do as neglecting hand techniques (rightly or wrongly, depending on what organization you belong to, IMO).
Pax,
Chris