Core Styles - Links Underlining

Why do all (the ones I checked anyway) of the Core style sheets specify
no underlining for links?

Although this is a trendy thing to do, and shows of the power of style
sheets, doesn't it set a bad example to new-comers to style sheets (i.e.
those most likely to use the Core styles)?

Isn't underlining of links something that, in most cases, authors
shouldn't be fiddling with? I make exceptions to this rule for things
like toolbars [1], but otherwise leave text-decoration to the user's own
preferences.

Or am I just worrying too much?

[1] where it is usually obvious that what is effectively a list is
indeed a list of links.

-- 
George Lund