If you're getting a newer system, then by all means do so. There is nothing wrong with Windows (even 8.x), and the choice of Windows vs. Linux is largely a matter of needs and preferences.

If you're using an older system, the options are much more limited. You may be limited to Linux or XP. While it is fine to say that people should upgrade, it is not a trivial decision for some people. Money is money, and people have priorities on how to spend it. Time is also time, and you can pretty much expect to devote a day to upgrading your OS by the time you install your software and transfer your data. Of course, there is also a learning curve involved whenever you upgrade.