Modern tablets contain compounds that react with grease and food bits to help lift the dirt. Washing this stuff off beforehand inhibits that reaction.
This was ages ago and I can’t remember if I was making it up or not.
All detergents contain compounds that react with grease and food bits to help lift the dirt. Washing this stuff off beforehand means there’s less to lift.
Modern tablets contain other stuff which negates the need for separate salt and rinse aid (though I suspect most people still add it anyway).
I can’t remember if I’m making this up or not either.