My earliest sparring sessions in karate were without the mandatory protective gear you see today. The only requirement was the groin protector; a mouthpiece was optional. By the 80s, foam head gear and hand guards had become compulsory for most schools per insurance purposes.
Probably the biggest argument against the use of protective gear is that it conditions the student to a kind of safety net that isn't always available. And yet despite this added precaution, the potential to get seriously hurt during a match still exists. In truth, the protective gear users may be instilled with a false sense of security and in turn feel that they have carte blanche to commit mayhem on one another. One article refers to this as risk compensation, which basically means we adjust our danger levels in accordance to so-called security measures.
The issue of protective fighting gear presents an interesting dichotomy. On one hand we have the time-honored body hardening techniques that are purported to forge our bodies into steel. I have my doubts, but you'd be hard pressed to find a Thai boxer who's heard of shin guards. Traditional karateka pound the makiwara (striking post) bare knuckled, yet Western boxers wrap their hands with gauze before lacing up a pair of 12 oz. gloves.
On Okinawa, karate fighters occassionally wear bogu, which is the protective armor used in kendo (sword-art). Bogu includes a chest protector and a full-face shield. Again, the idea is that players can go full tilt in matches without killing one another, try as they may.
The next time you train, try sparring without your fighting gear. It will feel strange and uncomfortable, and you'll probably feel reticent about loading up on shots. At the very least, it'll provide you with an interesting reality check.