A lot of the time people hire trainers just so they feel obligated to actually show up to the gym. Secondly, the avg 35yr old housewife doesn't know a single fucking thing about "working out". If they didn't spend an extra $250/month on a trainer, they'd be on the treadmill for an hour, then maybe muster up the courage to wander around from machine to machine doing 1 set of 20 reps on about 3 different machines before going home. Then after a year they'd wonder why they're actually in worse shape than they started.
Or, they (women) never touch a weight because they don't "wanna get to big. 90% of the women seem to think if they "lift weights" they're gonna somehow look like a man with a bunch of muscle. I have to point out about a handful of the neon-nike dudes and explain to them those kids are producing about as much testosterone as they'll ever produce in their lives (8-12mg... Maybe 700ng/dl), and they're doing everything they can to put on as much muscle as they can.. Protein shakes/weight gainer 3-5x a day.. Doing all the shit they read in magazines (or online), and training 4-6x a week and even with all that testosterone, none of them look like "bodybuilders".... Then explain that she (the lady) has about 20-40ng/dl testosterone. So if she somehow "turns into a bodybuilder" with her 3 30min weight training sessions a week, she has been born with 1:250,000,000 genetics and she will be the most famous female bodybuilder who ever lived and should embrace it.
Same goes for guys who say they "don't wanna get too big", as if they somehow have elite genetics that they're holding back from the world.
Take most people through a workout, even if they've been a member for a year, and explain why we're doing what we're doing,& ask simple questions about nutrition, and they quickly realize they're fucking clueless when it comes to excercise science and nutrition and realize why they don't look how they expected they'd look after joining a gym. Even if its a simple 1hr "session" a month to go over what they're doing and what to add/change without even "training" (basically just mapping out their "routine" and demonstrating the excersises and making sure they can do them properly& taking notes), they're better off than continuing to do the haphazard shit they've been doing.
A lot of the time I'd hire PTs who I knew clients would sign up with just because they looked the part, even if I had to write their clients programs myself. Ex-training partner/gf of mine was like that. She'd been certified about 6months but didn't really know what she was doing training-wise and her nutrition knowledge was "so long as its organic"-type shit. Started training with me and went from 113lbs to 127lbs in about 6months, going from a skinny-hot chic with 500cc implants to an actual figure-girl. Now she's since gone back to being as skinny as possible and pumping her natural/organic nutrition "brand", but successful nonetheless in orange county.... An ex-finance was the same way. Met her while the girl I just mentioned was visiting family in Europe. Hired her as a daycare girl and front desk, then took her test for her to get her certified as a PT and gave her the clients the previous girl Would've gotten if she were there. Quickly realized that even though she looked the part (1/2 Filipino with F'n great calves n legs. Flat stomach etc... And to this day probably the prettiest gf I've had. Us her brothers own an MMA gym in Atlanta & sister competes cross fit), she knew nothing about training ( while taking her through I work out I had designed for a client of hers, she was doing a close grip V bar pulldown and made the comment "this is for the chest right? Because I'm pulling to Bar to my chest?".. I had to look around and make sure nobody else heard and told her don't ever let anybody else hear you say that LOL).. But, she had a great personality and clients enjoyed her company so they actually showed up consistently.
You'd be amazed at the number of personal trainers that became personal trainers after only working out themselves 4 about 6 months and like somebody else stated above wanted to "share their Newfound love of fitness with others".
Typically speaking, bodybuilders make the worst personal trainers. Especially the guys in there early or mid twenties who dismiss all other types of training such as CrossFit and shit like that as "phag workouts" and wonder why their clients never make progress with the typical " arm day, chest day, back day, leg day, etc..." Routines... Shit that works if you're living a " bodybuilding lifestyle and using anabolics and such... But does Jack-shit for your typical gym-member who isn't using anabolics and only trains 3x a week for 30mins.