Can anyone explain why this works? Whenever I have a drain problem-sink or toilet-, instead of using a...

Whenever I have a drain problem-sink or toilet-, instead of using a drain introduction or calling the plumber, I use detergent and bleach in equal proportions- usually a measure cup- that come in some detergents. A relative have laughed at it ; but it works every time. Sometimes this relative uses the plunger and get hopping mad because of the time factor involved. When he fail to clear the drain, I get my detergent and bleach; and commonly I do not have to use the plunger. I know that nearby must be some scientific explanation or is this simply non-stop beginner's luck, a fluke etc? I own been doing it for years; and it works. Why?
How do I replace hinge on cabinet doors?
Answers:    Dont know the science aft it or what the bleach does, but an old neighbor who be a plumber used to pour straight industrial detergent down his own drains as " maintenance" & after he did a cleanout on the job.
Guess the out-of-date timers knew their stuff.
More prudence from the old timer that I still use, is to pour a bottle of dishwashing detergent down the sink from time to time overnight or if I'm away & later flush w/ hot water
Just soap & it sits here , works slowly & can't hurt anything.
He also used kerosene, but that would be enviornmentally incorrect these days.
Best regard
Does any one know?
I don't have an answer for you, except to voice that you need to pay attention mixing household cleaning products, especially bleach. Mixing bleach and ammonia will produce chlorine gas, which can be deadly.