Every day, many people will learn something for the first time that you had taken for granted for years. For some of these people, the thing they learned could change their life. (Here’s a fun thread illustrating this possibility.) 

Randall Munroe makes this point with this comic at xkcd:

There are some important implications here:

• If you think you’re too late to express yourself on a topic, or that there’s already too much noise, your opportunity is with tomorrow’s 10,000, or next year’s. You can say it your way (and say it again), and start with you. Find your quintessence.
• If you’re ever on the fence that something might be obvious, just say it anyway. I remembered saying this to a friend on a video call, who said they’d write it down so I figured I’d do the same. As it turns out, many people found it worth reading.
• You have much more to teach than you think; though the stuff worth teaching may not be the stuff you think is worth teaching. If you’ve said something three times recently, it’s worth writing about.