Well, more like there were no farms until farmers built them. A farmer is the labour and the management and the entrepreneur.
Your point about labour being so important makes it seem like having an idea and turning it into a business has no value.
Did you have an idea spontaneously or did you do the mental labour? Why is it so hard to get the idea accross that there is only labour in all the various forms. The meaning of labour is certainly not confined to the pick and shovel crews. So having an idea and building it into a viable business is definately labour. Find one business owner who will insist that he accomplished the task, whatever it was, without personal labour. The divison between physical and mental labour dosn't realy exist. Pushing a pen burns calories, very often lots of them. So the farmer and management and the entrepreneur are all labourers first and formost. And then we have capital which is not any form of labour whatever.