[RoboticWater]

The argument is two-pronged (probably more, but let's restrict it to two): firstly, yes, that diversity can improve gains, but secondly that the current skewed proportions were created by both active and passive discrimination which, to some extent, still exists today (though mainly in the passive form). Considering it from a purely utilitarian perspective doesn't quite do the issue enough justice.

It's essentially a moral argument: women and minorities deserve equal treatment and opportunity, but due to stereotyping and social inertia (i.e. girls don't grow up seeing many women in technical fields, so they aren't compelled or don't even think to join them), they don't currently get it.

To answer the question:

> Still, if women, men and people of different ethnicities and races all have such fundamentally different backgrounds, why would you expect them all to choose the same fields in the same proportion?

I think we'd like to assume that everyone can essentially do whatever they want, but just choose not to, but we simply can't because we've never had an equal starting position to begin with.