Bacteria can't be effectively washed off with water, which is why we use chemical abrasives and surfactants like toothpaste and soap when brushing our teeth or washing our hands. I don't know anyone who uses dish soap on their lettuce and grocery store outbreaks of food borne illness are a regular occurence, just not as sensationalized as the outbreaks at national fast food chains.
Hence the "effectively" qualifier. The physical force of running water is enough to wash off the top layers of microbes but even a small amount of bacteria can cause food borne illness so no matter what you do there will be a risk. If you dive deeper into the FDA recommendations there are toxicity reasons for not using soap or dish fluid and they actually recommend using a brush to clean firm vegetables and fruits because the abrasive movement is far more effective.
I recommend reading the CDC's studies of outbreaks which point out that in many instances the source is cross contamination of bacteria that can't be washed off due to specific molecules that adhere to the surface of produce. The CDC deals with crises and it's in a better position to study food borne illness than the FDA, which provides general advice with nearly a century of history tracing back to the progressive movement in the US. That advice is not necessarily up to date since our treatment of food has evolved to included irradiation, waxing, safety codes, etc. which get the vast majority of microbes to begin with.
my grandmother would always wash fresh vegetables in a potassium permanganate solution. i guess the practice declined as food was increasingly perceived to be safe
> Fruit and vegetable washes claim to kill more bacteria, but studies from the University of Maine have shown that tap water does as good a job or better. When produce is rinsed thoroughly, water can remove 98 percent of bacteria.
If you buy veggies, it's on you to wash them.
If you buy prepared food that includes veggies, it's on the vendor to wash them.