Simple - Because Linux distros aren't commercial products - they are supported and tested by a community of people who want to use Linux. It has nothing to do with professionalism, but a matter of choice.

I tend to think that the majority of Lenovo's customers could care less about having Linux on their laptop. Thinkpads have fast become the standard corporate laptop in the business world, and I think they are "OK", but not as impressive as their prices would suggest. I have a Dell and an old Gateway that run Linux at home, and most Linux users will put it on whatever they have anyway. Dell is actually doing fairly well, in fact better than they predicted with their Linux laptops, so all is not lost.