Windows 10 doesn't have IE 11 as the primary browser, and I'm not sure it ever has.
IE is there for compatibility in enterprise environments. There are a lot of large organizations which still rely on older versions of SAP, Oracle and IBM applications, plus whatever ungodly niche vertical apps or in-house garbage was written back in the 90s.
Microsoft has to cater to this environment because it's been the lifeblood of the company for ages.
It's not all doom and gloom, though. I've had experience in some very large organizations, lately, which prefer Chrome. The landscape is beginning to change, but it will be a while, still, before evergreen browsers are the norm in the corporate world.
