First, let me say that I'm approaching this from an average hobbyists point of view or capabilities, not just experienced people.
There are so many variables in the tank. Some people don't like a lot if rock, thus less bacterial population (if they're not using a marine pure or something similar).
Of course beneficial bacteria cleans, but the majority of bacteria is aerobic bacteria which just handles ammonia and nitrites.
You have to find a way for constant denitrification in your tank. How would you accomplish this without a dsb, or on bare bottom tanks? Most coral tanks have a lot of flow, so most of the rock work is getting oxygenated.
Yes you can add bacteria, but is there just a denitrifying bacteria? No. They're all pretty much chemical band aids for the main cause. Then you have people that constantly add too much and have bacterial blooms.
I have 2 big jars of CaribSea Rubble Zone in my sump. I drilled holes in the container so water could pass through and put it in a low flow area. That's not even helping all that much for denitrification.
Again, maybe this is a topic for only advanced hobbyists, but I try to look at things the average person would go about them. Most people don't even understand the nitrogen cycle. They just know you're supposed to replace X amount of water every so often.
