I've always had a gut feeling that if the best solution to a pest problem is to buy a $10 spray from Home Depot and spray it around your house in 10 minutes, a pest control company is never going to do it because it doesn't make them look like pros.
I wonder then which other processes are "held back" at a certain level of complexity only because if made simpler, the optics of the process would devalue the people who charge money to do it. Oil and filter changes?
I'm gonna have to play advocate here for The Institution over The Individual. The jobs you mentioned (pest control, basic car maintenance) exist because a lot of people can't be bothered to learn how to do it properly.
(Or, to put it more cynically: a lot of people are idiots. Like, a lot. Cue the quote about the average man and the thought that half of humanity is dumber than that...)
A lot of things can go wrong with the $10 spray you bought from Home Depot. You could end up spraying it where you're not supposed to and at best you end up poisoned in the ICU, at worst you contaminate your area's water supply. You could spray it on a lazy Saturday afternoon but you forgot about your dog who loves to lick the floor; at best you end up with a very expensive vet bill, at worst your dog then licks your kids in the face and you end up with a dead dog and a dead kid.
To be clear, I'm not saying your gut feeling is wrong; I'd probably do the same, honestly. But it most certainly doesn't apply to everyone.
Further, oil and filter changes might be super easy, barely an inconvenience but you could end up not resealing and tightening a valve or a nut enough and the worst time to find that out is when you're doing 100KPH on a highway. Don't even get me started about people who think they could save money by using olive oil where they are supposed to use a specific type of coating grease or lubricant; after all, they buy olive oil from the grocery once every month so, as a car maintenance item, it's "basically free".
These people are not only a danger to themselves. They are a danger to everyone they share a road (or a residential area) with.
Of course, having an industry around these tasks doesn't eliminate the possibility of these dumb outcomes but having "professionals" who are have read the fabulous manual and are regulated put them head and shoulders above J. Handyman Smith when doing said job. Emphasis on regulated, we give that far less credit than it deserves. You might have also read the fabulous manual but if you are not regulated, not beholden to a specific standard or process, how do I even check you didn't cut corners? If you mess up somewhere, how can you and everyone else even begin to assess the magnitude of your fuck-up and thereby respond appropriately?
This is true but kind of tangential. My point was even for the pest control company if it were a 10 minute job, they wouldn't do it that way because the "spectacle of professionalism" that justifies the prices they charge (and perhaps recurring revenue) is lost.
For oil changes it is completely conceivable for a user-serviceable system to be built in, making it not much more difficult than filling air in your tires at the gas station. But the manufacturers have a perverse incentive to not build it.
If that was the best solution then the pest control companies would do that, except they'd try to buy the spray in bulk straight from the supplier and use their own permanent spraying devices instead of buying a series of cheap disposable cans that force them to bend over all the time.
To some extent our notion of what's "professional" is dictated by past experience of professionals using what works best for professionals. If that changes, an unofficial pest control business has a pretty low barrier for entry considering there are literal DIY solutions at retail.
I wonder then which other processes are "held back" at a certain level of complexity only because if made simpler, the optics of the process would devalue the people who charge money to do it. Oil and filter changes?