I can't fairly speak to their support quality (having never bought their products, and as someone who sees a fair bit of their money come my way for marketing) but:

- I would have thought most people currently buying linux PCs don't have the same support needs as those buying Windows PCs (generalisation obviously, but lowest common denominator and averages)

- For Dell products at least, support is a paid-for extra that you can add on when buying (at least for OS-level support)

- I wonder how the costs would balance out between needing staff with new skills and saving money on Windows licenses