Biological material like blood, bodily fluids, and sewage can carry bloodborne pathogens and bacteria that survive long after a surface looks clean. Wiping it up with paper towels and a household spray spreads it around more often than it removes it.
Professional biohazard cleanup starts with protection and containment. Technicians wear respirators, suits, eye protection, and gloves, and seal off the affected area so contamination doesn't travel to the rest of the home.
Then the contaminated material is removed. Porous materials like carpet, padding, and drywall often have to be cut out, because fluids soak deeper than the surface. Hard surfaces are cleaned and then treated with hospital-grade disinfectants for the correct contact time.
Finally, contaminated waste is bagged and handled separately from household trash, and the space is deodorized. For families, the most important part is often not having to see or handle any of it themselves. That's what a professional crew is for.