You will become a better writer. Writing is a means of communication and your communication will get better the more you engage with writing. Writing consistently will sharpen how fluently your thoughts are transferred to pen and paper.
You will learn more than you ever imagined. Blogging will get you exposed to new information in your niche and you may also pick up some valuable new skills for yourself.
It boosts your confidence level. When you offer value and people get attached to your blog, you feel important and needed.
You will be exposed to new people. One thing blogging does is make you relate with people you may have never met. It could be through blog comments, email replies, or from social media.
Down the line, there are financial benefits to blogging. It could come through affiliate marketing, sale of digital courses etc. but blogging can be extremely lucrative.