- smells
- dirty laundry
- Comfort (not wallowing in your own filth)
- sweat does tend to flow.. bringing with it.. you guessed it.
But onto your point about "disinfection". I don't know which alcohol baths you take, but full disinfection isn't the goal. But since you need evidence.. "How effective is soap over plain old water? It works, but all else being equal, water has a greater marginal effect. " [1]
[1] https://www.theatlantic.com/health/archive/2012/06/soap-how-...