Other - why is two factor authentication very important to all Internet users?

Why is two factor authentication very important to all Internet users?

According wikipedia, Two factor authentication means that "is an approach to authentication which requires the presentation of two or more of the three authentication factors" Why is it important to enable two factor authentication in these websites such as the Facebook and Google? If you have password only, your account might be getting hacked even if your password is so complicated.

Enabling two factor authentication will reduce the chance of the hacking because the hacker must have your cellphone or specific application to hack your information. It will protect your encrypted and sensitive information like credit card information, personal information, and etc. 

What website has provided two-factor authentication?

Website Service Provider and Social Media

Google (included Youtube, Google +. Blogger, and Google Drive)
Facebook

Microsoft (include MSDN, TechNet and Outlook.com)
Apple / iCloud
Twitter
Cloudflare
Hootsuite

Web hosting:
Linode
Dreamhost

Cloud Service:

Dropbox
SpiderOak
Box

Online Shopping:
VeriSign Identity Protection Access (Paypal, eBay, VeriSign Personal ID Portal)

Managing personal matters:

LastPass
Passpack

Amazon Web Services

Online Gaming:
Battle.net
MMORPGs

Security Question Only:

Yahoo and most bank website - Security Question but it is not safe because if it is an easy answer, the chance of hacking will be higher. However, Citibank and Bank of America have introduced 2-step verification recently.

In the inclusion, two factor authentication will be useful if all of the websites are providing that. However, you have to enable it because it is optional. If anyone knows any websites are providing the two factor authentication, please comment this post.