Hold on a second, chums. Look at that screenshot again. That's the opening scene of Half-Life with subtitles. Pretty important atmosphere-setting, isn't it, that train ride narration? It makes Black Mesa seem so much bigger than us. Half-Life used an awful lot of speech to reveal what was going on, from our one-sided conversations with scientists to soldiers yelling at each other. Here I pull off an incredibly adept pull-back-and-reveal: those subtitles were added by a mod which only came out this year. A new version's now out, with new ways to make this side accessible to folks who can't or don't want to hear it.
As well as, obviously, adding subtitles for all the dialogue in several languages, the mod tweaks NPC AI to stop them ruining things. They won't blab their random barks when someone's saying something more important, for starters, and are less likely to interrupt each other in general. A more polite Half-Life. Only speech within earshot plays subtitles too. The creators last week released the beta build of version 3.0 over here. Earlier releases were functional, but this sounds (hilarious, Alice) a lot more polished. While they were at it, they also fixed a few long-standing Half-Life bugs, so it's built on a more solid foundation.
Valve's closed captions are pretty great and comprehensive nowadays, though.
But gosh, I feel silly only now thinking what Half-Life is like without speech. Some scripted parts must be baffling. All the little objective reminders from NPCs are gone. That iconic train ride must be a little boring ("It's pretty boring for everyone else too, of course," adds our John, the wag!). Gordon's continued silence might be puzzling.