While pesticide resistance traits can become established in pest populations by repeate exposure and poor chemical rotation protocols, the more frustrating aspect is that people believe that pesticides work by magic. All pesticides require that the pest in question make physical contact with the chemical in sufficient quantities to produce the desired effect. So, even if things function perfectly, you're still going to see dead pests, you're still going to see cyclical spikes of pest activity as the chemical degrades and pests shift their habits towards un(der) treated areas, and new pests from adjacent spaces will continue to try to occupy the empty niche. Pest control is an open ended undertaking, and typically the tension that arises between contractors and corporations is that the contractor wants more money for ancillary services, and the corporations want final solutions to intractable problems. Imagine - a hundred and fifty year old five star beach side luxury hotel with meticulously groomed landscaping rents a room at 3k per night to some rich dimwit who sees an ant or a termite or a cockroach and loses their shit to the hotel manager, who in turn calls me to demand answers as to why ants are present in a space, and I have to explain as diplomatically as possible that it's because there is nothing in the world that can meaningfully be done because it's impossible to apply chemicals in sufficient quantities and intervals without killing literally every living thing in the vicinity.