This is a weird question but....

In my game my stoves, counters, tubs, sinks, showers, toilets all get dirty at some point. Some more frequently than others but nothing out of the ordinary. That's funny that some people have never had the stoves get dirty. I usually notice something is dirty when my sims get the filthy surroundings moodlet. I will say, sometimes the darker your counter & stoves the harder it is to see the grime.