I presume that Microsoft has found that home users value having a cheaper PC with ads, over a more expensive PC without ads.
Similar to Gmail and the likes of numerous SaaS companies. There's a freemium version with ads (or some type of limitation) or a paid version without ads (or said limitation).
Basically, tell an ISV (like Connection.com) that you want a small business relationship w.r.t. Microsoft Licensing and they'll set you up. You might have to buy a few random CALs to qualify, but it's totally possible and a godsend.
Similar to Gmail and the likes of numerous SaaS companies. There's a freemium version with ads (or some type of limitation) or a paid version without ads (or said limitation).
Just playing devils advocate here.