This won't happen for a very long time for the exact same reason we are still wearing a uniform shirt designed in 1920 and pretty much the exact same uniform that the US Navy has worn for around a century: 55-65 year olds are making the decisions and throw out the need to look "professional" even though it looks dated and downright sad on some of the physical specimens that inhabit US airline cockpits.
Look at VAs uniforms. They are sharp, modern looking, still conservative, yet somehow both comfortable and functional (and going away soon). Customers love them. The pilots that I have talked to like them.
The beard rule is dumb, the bus driver/ship captain uniform is horrible, but until there is a big movement to change it, it's here to stay.