No they don't... it's a fact, no matter how popular your page is, not all of the fans will see your posts. Never! Even if they all participate, they still wont all see your posts - which is highly unlikely. The only way to reach them all is to pay to promote your post & even then - you'll need a huge budget.
Absolutely yes, here's my top 2 reasons: Give consumers confidence in your product. Build your brand's reputation. Give you the ability to have more people see your posts - even if you only have 10% reach. 10% of 100 is 10. 10% of 1000 is 100. Make sense?
I don't know others but I cannot see any real value. I don't see increase on the site visits or anything while I have likes.