Yes I know that but normally you would expect a union to stick to that industry, also blue collar unions don't always know how to organise and represent profess

Yes I know that but normally you would expect a union to stick to that industry, also blue collar unions don't always know how to organise and represent professional workers and some members may not want "their" union to represent mangers eg the CWU in the UK Trying to go back to the ancient one big union just wont cut it