Unfortunately, selling has become more important than the actual training these days. Especially working in the commercial gyms. I have seen many trainers that are just terrible at the training side of the equation. I stand back and watch them train from a distance, and they end up having the clients work out their mouths more than their bodies. Just terrible. However,they are excellent sellers. They manage to get re-signs over and over because they are good at small talk and selling people.
With me it is the exact opposite. I am a good, high quality, trainer. I am extremely knowledgeable, I continually update my education, and I am very creative with my program design and training methods. However, I suck at selling. I train at a facility where the demographic is very cheap. The monthly dues are EXTREMELY low and the training sessions are priced very high. Especially for the area that the club is in. So a lot of people get turned off by the high prices. I have given out so many first workouts where the person loved me and my training style and wanted to take it to the next level, only to be turned off by the prices.
Another bad thing, is that the higher end facilities that favor training over selling all want Kinesiology degrees along with the certifications. I have 15 years of experience and knowledge in health/fitness along with two certifications - NASM and ACE (the two most recognized). Yet I can only get work at the commercial gyms because I don't have a Kinesiology degree and most commercial gyms are like used car sales jobs in regards to the training. Unfortunately I just don't have the money to go back to school.
So unless you have the money to get a Kinesiology degree, definitely learn how to sell. You will need the selling skills.