Because when you need to optimize your system, as you might want being a trader, it is almost impossible to discern the different interactions between IE and your OS. Unexpected things happen and expected ones don't. Stuff from Microsoft never works lean and mean nor clean. Install Office and your whole system setup has changed. Try installing drivers for Microsoft mouse or keyboard and you might have to rollback a system restore. It's bloated and it's bad quality. FF is sold by technicians, IE is built by salespeople. Ursa..