A little history,
OK, first am not a fanboy, I use Windows and Firefox on an IBM PC clone.
1, Lets look at purposes, Internet exploder was purchased and integrated into Windows 95 with the intention of killing Netscape. Microsoft saw the browser as a potential platform capable of running applications which may have hurt it's cash cow Office and other Microsoft programs.
2, Microsoft used its position with it's dominant browser in its usual manner, embrace, extend and corrupt... standards got ignored.
3, If you don't have a default browser installed.... its simple, to all of you too young to remember FTP, a simple script and a call to the relevant FTP site (implemented to be easy for the user) will bring you IE, FF, Opera, Safari, Chrome or whatever you wish to use. No need to have a browser loaded by default on installation.
4, To those bleating on about Apple Macs being closed, the pc was closed initially even thought the hardware could be bought off the shelf. The BIOS was wholly proprietary to IBM.
Microsoft had the genius to arrange for a license to produce DOS for its own purposes.
Compaq (I think) worked to reverse engineer the bios code, and marketed a CLONE pc.
Because of the Microsoft DOS license an OS could be legally procured. Had that license not been in place the IBM PC XT/AT would STILL have been closed.
Apple have retained control of their hardware and OS. No external licence, no third parties able to independently make Mac clone PCs. OSX is their program, Apple can do with it as they wish, there is a strict limit on the hardware that the OSX license approves. Apple hardware ONLY. Bleaters, get over it.