Ever notice how convenience tends to trump sanity? Like, little bits of plastic in your bodywash, so that you don't need a washcloth to exfoliate? Like bodywash in a plastic 'recyclable' bottle so you don't need a reusable container for a bar of soap? I know, the advertising and packaging of bodywash is much more seductive than the wrapper on the bar...
Excess soap itself is a pollutant. People are much less likely to use too much when it is a bar of soap. Liquid soap in shared facilities makes sense. The rest of the time, it's style, not necessity.