keep internet explorer - you won't regret it, and you don't have to use it as a day-to-day browser.
as others have said, many other windows and third-party software rely on the ie trident engine, such as steam and winamp, amongst many many others. it saves those programs from having to write their own browser to show webpages.
(@marsmimar outlook and word use their own html rendering engine which is flawed and buggy
- if only they would use ie!)