Most definitely not.
You really only need to be on the platforms your ideal customer uses.
What if I don't know what platforms my ideal customers use?
This is where a little bit of research comes in handy. If you have gone through the steps to identify who your ideal customer is, you probably have some good demographic information about them.
Say, for example, if your ideal customer is a college educated middle-aged male with an income over $75k, you would likely not want to use Snapchat. The key demographics for this customer rank very low for Snapchat. However, Facebook and YouTube rank high for this customer.1
Similarly, if your ideal customer is female between the ages of 25 and 54, Pinterest may be a strong tool for you to use. Pinterest reaches 83% of all women 25-54 in the US.2
It's not just demographics
The type of posts you are making are also important. Kinda obvious, but you wouldn't post a photo to YouTube. Wrong platform for that type of content. You have to take this into consideration as well. While most (all?) platforms have embraced video in some form, people would not expect to see anything other than a video on YouTube.
You also want to look at the space you are targeting. If, for example you are in the B2B space, you would probably want to have more use of LinkedIn. Contrarily, if you are in the B2C space, LinkedIn may not likely be the best platform to use.
There are a lot of variables to what is the best social platform to use. You do not need to be on all of them. You should use some of them. Test different campaigns on the different platforms - as well as on the same platform - and see what gets the most traction.
- Pew Research Center, https://pewrsr.ch/2VxJuJ3
- Hootsuite, https://blog.hootsuite.com/social-media-demographics/