Why do they always claim they "can't wash off" the scent when soap literally exists?! 🧼🚿

In almost every urban Omegaverse or fantasy setting, a character will spend an afternoon in the same room as the ML. The next morning, every side character on the subway is gasping, holding their noses, and asking: "Why do you reek of an Alpha's dominance?!" Did the MC not shower? Did he wash with water only? Is standard shower gel completely useless against fictional pheromone particles?!

What is the silliest explanation an author gave for pheromones lingering for days?