End users do not get to chose what application developers develop for. Working in an heavily FDA regulated environment, Internet Explorer was in fact the only supported browser allowed so that is what everyone used. Sometimes design requirements are not just because a developer is stupid or they are too lazy to develop and application that works on multiple browser platforms. Often it is dictated by the requirements put in place by an organization or management and there is no element of personal choice.
I would love to be able to use something besides IE for a great deal of the work I do. For some things, I use Firefox and Chrome when possible but there are simple some applications that I use at work that do not work well in IE. Their functionality is crippled by using a different browser and I, for one, will not give up function just for the sake of having a different browser. Hell, if I really had the choice, I would run Linux at work but I need the .NET Framework and IE. Everything else would just be a hassle to get working when Windows just works. It all comes back to using the right tool for the job.
Sorry, I realize this is off topic but I can fully understand why some people really do not have a choice but to run IE in certain situations.