A single tank scuba diver takes up one boat spot, but a technical diver takes up 2.5 spots. Technical diving has enjoyed a good safety record, which is to say diving incidents share a smaller piece of the pie than nontechnical dives. However, technical diving accidents usually get scrutinized more because they involved more risk. The potential for training accidents is much greater than in most other types of specialty training. This is a real concern for instructors.
Equipment plays a significant role in technical diving.
It is merely not enough to have a personal diving rig and a stage bottle or two. The technical diving instructor needs to be fully familiar with all the gear available, own the best possible personal gear and have a full set of back ups. When students make the commitment to learn technical diving, the instructor cannot afford to have a dive washed out because a piece of their equipment went bad during set up. The instructor needs to be able to make the dives happen with appropriate backup gear. The time and boat fees just cost too much to waste.