The big hospital I go to (for now-twice-yearly tests) want to minimize patients (because wait times are long and they have too many patients). That is why most big hospitals want referral letters -- otherwise they charge you a big "first-time" fee.
When my local clinic told me to go to the big hospital in 2021 (to get serious tests and then some surgery), the hosp doc then gave me prescription for 2 extra meds for 60days, but when I asked him to give me a presc. for other meds that my local clinic was giving once a month, he said no -- I should continue to get them from the clinic.
I found it complicated juggling 2 sets of meds from 2 different docs for different periods. But I understood the hosp doc didnt want to pull any business away from the clinic. When he decided my condition was stable after a year, he transferred all the med prescriptions to the (monthly) clinic.
I guess small clinics and docs advertise for business, to get more patients. It would be tempting for them to maximize treatment, meds, and patient visits. I guess some of them dont do it, but others do.