Because the smell is no longer coming from the waste. Bacteria and the ammonia and sulfur compounds they produce soak into the thatch layer and the top inch or two of soil, and they stay there after the solids are gone. Chattanooga humidity keeps those compounds volatile so they keep lifting off the ground, and our clay-heavy soil drains slowly so what soaks in sits near the surface.
Remove every bit of waste including the flattened pieces along fence lines, get the bags off the property rather than leaving them in a bin, then water the affected areas heavily. A deep soak dilutes the odor compounds and carries them down past the root zone instead of leaving them at the surface. Give it two or three days. For a yard kept up on a normal schedule that is the entire fix, and it costs nothing but water.
Garden lime raises soil pH and can reduce ammonia odor slightly, but it is not an odor treatment, and overapplying it damages the lawn and is not something you want dogs walking through. Water is more effective, cheaper, and cannot hurt the grass. Scented sprays only mask the smell for a few hours, and bleach kills grass, is unsafe around pets, and runs off into storm drains.
Scoopy Doo charges $20 per visit for deodorizing and sanitizing, and it can be added to any recurring plan or to a one-time cleanup. It neutralizes the odor compounds and bacteria in the soil rather than masking them with fragrance, and it is safe for pets, children, and lawn health. It is worth paying for when a yard has years of buildup, when one area takes nearly all the traffic, or when an event is coming up and there is no time to wait for watering to work. For a yard on a weekly or every-other-week schedule you usually do not need it.
Odor is a symptom of accumulation. A yard cleaned every week never builds up enough in the soil to develop a smell in the first place. Weekly service is $20 per visit for the first dog and every-other-week is $33 per visit, neither with a contract. If the yard is badly behind, start with a one-time cleanup from $85. Free quotes at scoopychatt.com/quote.
That is urine, not waste, and scooping will not touch it. It is usually worst in one small patch with yellowed grass around it. The fix is the same first move: soak it heavily and often, because urine salts are what burn the grass and dilution is the only thing that moves them.