It is not a must to introduce yourself, but it is recommended, so people know your values, and what you are looking to do here on steemit. The more value you will give, the more other steemit users will be interested in following you, and/or read what you will be doing on future posts.
If you decide to do so, add the tag "introduceyourself"
Also, check 
RE: Chapter 1 of 11: Have you recently Sign up on Steemit and Don't know what to do First - Basic Things for New People make their way easier on the Platform - Part 1: What you need to know to be more confident & get rewarded on the platform?