Why do they need to dress for the corporate world (which has largely opted out of suits and ties anyway)? Those who do enter the corporate world will likely be going to university anyway, with no uniform obviously.
And you do realise that countries with much larger corporate sectors than the U.K., such as the US and Germany, have no school uniforms at all? They manage to dress appropriately.
No uniforms or dress codes in any of our sixth forms here, which are some of the highest performing in the country. It would be bizarre to see the students in “smart business wear”, like junior estate agents or something.