While this thread was going on, another user and I were taking the MS Sans Serif font in and out of our computers to try to troubleshoot another problem. I don't recommend it.
But it seems that the reason MS Sans Serif is used so universally is that it both looks good and uses relativley little space in Windows boxes. In Foxpro, when you substitute another font to get a different character set, the data boxes that we type names, places, etc. into expand to include the larger substitute font. UFT gets a lot less user friendly as a result, but it does continue to work.