What keeps bullpups from being superior to guns with conventially placed magazines?

The only disadvantage to a bullpup that I can think of is that might take longer to reload.

I do not find bullpups harder to load; the only disadvantage I see is that you cannot use iron sights. Optics tend to get broken, I am an old guy that likes to have an iron sight backup.

On the SA80 there are iron sights and even on the SUSAT itself there is an emergency battle site on the top, and as far as i remember on the steyr aug there is a battle site on top of the optics as well. I dint think the loading of the weapon is much of an issue compared to the convential rifle design.