it's included as part of the MS Windows O/S (the same way as the worst browser ever made was, i.e.: I.E.)
Nowadays it is called Edge and is a much better browser. Believe it or not some of my Mac based programmers use it as a default, since it is a Chromium browser with decent developer tools.
I'll give you that it is still tied into the Microsoft OS for some compatibility reasons, but IE is going away (finally).
From MS -
'The Internet Explorer 11 will be retired and go out of support on June 15, 2022. '
You can still install it until then, but there is a light at the end of the tunnel. <grin>