A question about Islam?

As i have lived in Pakistan for a few years in my life as part of business i have learnt a lot about their main religion; Islam and their culture. I have some understandings as i mingled with locals and colleagues (when in rome do as the roman do). Many men dont allow women to work and say it is against their religion; Islam. However, i have learnt that your Prophet Mohammed agreed to marry a 40 year old successful business woman when he was 25. She carried on being a business woman even when she was married. To me this indicates that islam does not discourage or forbid women at work or in business. Do you think it is a cultural aspect then as i have come to understand it?