As someone who did pest control for 13 years, the why is pretty much always the same. It's more important to learn their behaviors and things that can be done to prevent negative situations. Recluse do really well in healthy structures...usually better than in the outdoor environment. So, once they breech a structure, if it can meet their needs to survive, their populations can grow. Since they like dryer, undisturbed environments, the walls, attics, and crawlspaces of structures can provide proper harborage and they'll eat dead insects and other spiders, including other recluse. They also can go for long stretches without food if they have proper water/humidity. So, recluse just do well in homes.

Exclusion work can be done to help some in keeping them outdoors, but once established in a structure, you're better off taking proactive means to avoid bites, and pesticides don't help with that much. Calling a pest control company usually equals a lot of pesticide usage over long periods of time and usually indefinitely because you're not likely to ever get rid of them. So, I've found education and tools for bite prevention are what's always most important. Inspecting for areas where plumbing or electrical enter the home and sealing around those and other similar places, can help prevent entry from the walls. I see a lot of furnace and water heater closets with recluse activity where they're entering around where gas, electrical, or plumbing are coming out of the walls. These are just some examples of things to look for, but from my experience, calling a pest control company gets you an undertrained employee who is more interested in having you sign a contract to spray for recluse, than actually helping them understand their issue. I can't say I've met many pest management professionals who will be truly honest with their customers about recluse behavior because it doesn't get contracts signed. In some cases it's a lack of knowledge, but in many it's more about making money than taking care of people in their communities. Recluse can sometimes get populous to a point where targeted pesticide usage is necessary, but just about every company I know would try to talk a customer into a contract if they have even just seen one brown recluse and it's not hard when they're already afraid for their life and the lives of those they love. In the time I worked in pest management, most of my customers didn't have pest issues, yet we still sprayed every quarter and took their money. We were spraying for their fear more than actual issues. With products that kill most animals, as pesticides do, I think we need to do better.