Great minds think alike: My mother just finished telling me that she uses the baking soda every month in her drain.
She says she would *never* put grease down a drain. She knows from experience how expensive it is to have to replace a septic tank drain field that has become clogged with grease.
Yes grease does reach the septic field, once the tank fills up and the grease layer at the top of the tank is thick -- I had my tank repaired a few years back. It was very close to clogging the drain field.
And that's just pan-wash of grease. So grease makes it past the sink traps.
In a public sewer system the grease will collect at pipe restrictions, baffles, and turns especially where the point is cold enough to turn liquid grease into a wax.
Congealed fats are mostly the result of meat wastes; vegetable oils will not congeal as readily as lard, suet and tallows.
Established communities of any great duration are full of old wastelines that have sclerotic pipes from iron oxidiation and clay-pipe decay.
The worse this condition gets, the more clogging from greases and fibrous waste becomes.
Everything needs maintenance and eventual replacement.