Why? It has its benefits too. For example it can reduce viral load in the mouth, reducing the risk of COVID transmission for example. I think people can make their choice as to what product they want to use and what tradeoffs they are okay with.
Consumers often don't make rational well informed choices though; the nuance that alcohol based mouthwashes both dry the mouth -- and, possibly correlated -- that this study show, leads to proliferation of bad bacteria biomes should be able to at least lead to removal from the recommendations from the American Dental Association.
In regards to benefits, peroxide based mouthwashes do have similar lysing effect but less drying effect - and this has been known for ~ a decade; and fluoride mouthwashes should actually activate the salivary glands, in addition to lysing. But, one could speculate that peroxide based mouthwashes would have a similar result to alcohol based in this study based on what we know about wound care (that peroxides kill both the bad and good bacteria)
Do you have any papers or studies showing it can reduce transmission of any disease? Covid lives in the throat and lungs so I am not sure how a mouth rinse could do anything. Similarly for many other common colds and the flu.
I did a quick search and there are numerous studies that come up. I haven’t analyzed them myself, but it seems like there is a lot of evidence for this (example https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8956107/). I also found various things written about covid living in the mouth and playing a role in transmission.