If you intend to run Windows, then I agree with you.
But if you don't intend to run it for whatever reason, then why should you be forced to support that company by obtaining a license from them?
I don't write "buying" because it's usually not a matter of financial cost, because as others have pointed out it's sometimes even cheaper to get a computer with a Windows license.

It's a matter of free choice. MS assumes that every license they "sell" is a computer that's running Windows. That's not true and they know it. Nevertheless they use these statistics to strenghten their market position, because hardly any computer seller will risk to lose his deal to get the MS licenses basically for free.
Imagine you're vegetarian by conviction! Would you accept to have a "free steak" forced on you in your grocery store or otherwise you are not allowed to buy anything there? I don't think so. So you'd just go to another grocery store. But what if it's hard to find a grocery store that doesn't have this policy, and the few that don't have it only have a very limited range of (even vegetarian) products?

I'm not saying everybody should abandon Windows. If you have a use for that OS, by all means, use it!
I just don't want it to be forced on me. And that includes the very first step, my choice of obtaining a license in the first place.