fumigating houses, pest control at commercial food facilities, commercial premises etc is a big dirty difficult job and involves expensive equipment and hazardous chemicals etc plus as OP noted requires exams before you can do it for 3rd parties

I think you're assuming that there is no valuable/monetizable difference between a neophyte, and an experienced expert serving (and supported by) a solid organization.

Also, I don't know where you live, but the more powerful substances used by licensed pest control are regulated and aren't (legally) available to the general public. If you're willing to run a business model based on unlicensed use of controlled substances, there are more profitable options than pest control lol

My biggest problem with a service like pest control is I can't tell what it does. I'm not talking about getting rid of a hornet nest or squirrels in the attic, I'm talking about the door-to-door salespeople who want you to subscribe to a quarterly sprinkling of some magic dust around your house. If I could get a trustworthy measurement like "number of 2x4s not destroyed by carpenter ants" or "sqft of siding not rotten because of nests" I would be a lot more open to it.

For the d2d residential services, you're buying peace of mind and usually the provider will guartantee the service. E.g. if you see ants and you're not due a visit until next month, they'll drop in and sort it.

On residential - lots of people don't want to get their hands dirty. For commercial - it's rarely worth doing in-house and in manufacturing / food industries getting it wrong can lead to fines / closure losing contracts, so it's not worth penny pinching.