First of all, I realize that styling in HTML should be handled by CSS, and I don't want to change that.
I just want a solid tag I can use for underline, a tag that is meant for underlined text, or one that makes sense to use as such. Then I can style it with CSS.
Now where is that tag?
Why is strong, b, em, i etc. perfectly fine (and often auto-styled in browsers), but underlined is the forbidden fruit?
I would hate to write
<span style="blabla: underline">some underlined text</span>
OR <span class="underlined">some text</span>
when I can just use
<u>hello</u>
and style it?
The u element was meant for underlining, ever since HTML 3.2. HTML 4.01 frowns upon it by “deprecating” it, and HTML5 proposes to redefine its meaning in an obscure manner. Yet, in reality, it works in all browsers, and will keep working, and has the exact effect of underlining.
Whether you should underline anything but links on web pages is a different issue. So is the question whether you should think in terms of logical structure rather than visual rendering.