10 Reasons Why You’ll Be Using Google Plus In A Year put out a great list and explanations of this subject. I’ve made a summary of them here with my notes, but go check out their site for the reasons why these 10 make sense.

10 Reasons Why You’ll Be Using Google Plus In A Year

1. This Time Google Is Serious. Google did an incredible job incubating with influencers and have a very open dialogue and listening to everyone.
2. Google Owns About 23% of Browser Market. The ability for developers to quickly build integrations in Chrome with G+ is awesome.
3. Google Owns Android
4. Google Owns All The Tools Competitors Want Or Are Flailing To Acquire – The Youtube integration is a super cool feature for adding videos to a post.
5. Google Owns Business Applications And Servers
6. Google Owns Search. The SEO of being able to have your posts searched on the internet is huge.
7. Making A Connection Does Not Require Approval From The Second Party. Publishing to public or sending to the Friends in your Extended circles helps draw new followers.
8. Circles are Mandatory On Plus, Which Will Feel More Comfortable. Circles rock as a way of Grouping.
9. Google Can Afford to Let Plus Be Just A Social Network. All of Googles other products benefit new users from Google+.
10. Everything on your account is exportable—in an obvious way