Windows comes pre-installed on PCs when you buy them because it’s what people are generally comfortable using, because it’s what they use at work too.
And Windows is used on business PCs largely because of how manageable they are at scale. Windows is expensive. Like, really expensive. If you have 1000 PCs that have Windows and Office E3, assuming a bulk discount, that’s an up front cost of ~$200000 with the subscription costing an additional ~$20000/month. If it was feasible for business to change to a free alternative, I guarantee they would’ve done so.
You’re right in that that Windows is not some super great OS, but it does some things way better than anything else that make it an ideal choice for business use.