Some reasons for you to use your microphone.

You jump into a game. What game? Any game, you’re not fussed. But you jump in, ready to push a cart and capture the control point, and it’s deathly silent. No, the server isn’t empty, in fact, there’s 23 players running around like maniacs. But NO ONE is talking. And that cart hasn’t moved for a good three minutes.

Time to get the microphone out! What? You don’t want to? Then shut up and read this thread. Oh, and plug your microphone in.

Reason the First: It’s a billion times easier to tell your team that there’s a sentry ahead.
Sentries are one of the biggest nuisances in Team Fortress 2, often slowing a game to a standstill. But not everyone can see what you can see, so if you’re the first to spot one of these bastards, call it out to your team mates. The same applies to pretty much everything else. Did you get backstabbed? Tell your buddies. Is there an Ubered Heavy around the corner? Tell your team to wait a few moments before charging in. Your team won’t die as much if they know what they’re about to run into.

Reason the Second: You can tell your team what to do.
If there’s only one person speaking, people will listen. Alright, people won’t always listen, and they may flat out ignore you, particularly if they don’t speak whatever language you’re speaking, but at least there’s a much higher chance of your team gathering around you and working as one coherent force if you use your microphone than if you just follow as one of the silent masses. Even if a few of you are talking, it’s a far quicker way of sending information to one another than sitting down and typing it all out. If you’re currently losing badly, perhaps the enemy team is already employing this strategy.

Reason the Third: It’s easier to berate… um… I mean, advise your team mates when they suck.
Sometimes, your team really does, utterly and totally suck. There’s no getting around that. Your team mates might be so stupid that they’re running entirely the wrong way. Or entirely the right way, because it means they’re not dying. If your team mates are that unreasonable, they’re not going to listen to some voice commands or some text. Either way, using your microphone to tell them what they’re doing wrong is far superior to simply carrying on as normal.

Reason the Fourth: Conversation is fun.
The sound of recently gibbed Medics may be amusing for a while, but if there’s no witty banter coming from behind both the Gibber and the Gibbee, there’s a huge missed chance to make even more joy. No one to congratulate you on that great kill, no one to say thanks for healing them, no one to whine because they got killed by that damn Pyro again, no one to cry about the Rocket Launcher being overpowered. Team Fortress 2, like most games, is all about interactions, and the silence of the average server just feels depressing.

“But Medic! Everyone complains when they hear my voice!”
You know what I say to that? CRY SOME MOAR! I have had loads of complaints about my voice, because, despite being a woman, I sound like a little boy (apparently…), but does that stop me? Nope, even if it means me being banned from the server. People have personal mute buttons for a reason, so if they don’t want to listen, they can mute you themselves, and miss out as you lead your team to victory. Alright, sometimes, your microphone is evil and makes nasty noises, so maybe using your mic then is a bad idea, but nonetheless, if you have a working microphone and a slither of self-confidence, help bring victory to your team!

“Medic, I don’t have a microphone!”
Ah, well, that’s an issue. Maybe you could get one. They’re not that expensive. Heck, look on somewhere like Ebay or Amazon and you’ll probably find one for the same cost as a couple of keys.

“I really don’t want to talk…”
If you’re really not in the mood to talk, well, don’t do nothing! There’s always voice chat and voice commands! Some voice commands are more helpful than others, particularly the MEDIC!, Help! and Incoming! commands. The Spy! command is also useful and is great for spamming just to keep your team on their toes. If you’re not very fast when it comes to typing, why not set up some key binds to do the typing for you? I’m not talking about trash-talk binds designed to annoy, but binds designed to help. Remember, you can always make a bind by typing bind *yourkeyhere* say_team “Your message here!” either in the Developer’s Console or your CFG files.

So, that’s it, some perfectly good reasons for why you should use your microphone. Remember, teamwork and coordination win games, and talking helps!