Virtual worlds can be used for entertainment, training, psychological healing, virtual business and school meetings, etc.
In the article After Second Life, Can Virtual Worlds Get a Reboot? by Diane Mehta you learn that children 5-15 have created half of the 2 billion accounts registered on virtual worlds. Since it is easier for children to go online than hang out outside they have turned to virtual worlds for entertainment and friendship. The article also talks about how virtual world designer and Senior Scientist and Project Director for the University of Southern California Institute for Creative Technologies Jacki Morie creates virtual worlds to train and heal military personnel. In the article Going to the virtual office in Second Life by Mark Tutton talks about how virtual meetings can cut company costs by allowing different branches in other states to meet without having to travel.
The biggest pro of virtual worlds is how quickly and easily they can bring people together. Instead of having to wake up, fix your face, get yourself dressed, and travel somewhere you just have to turn on your computer or pic up your phone. The biggest con of virtual worlds is how easy it is to loose yourself in them. You spend time creating your avatar, and sometimes updating it or changing its outfits/accessories. You may start building relationships online with other people and they become part of your life and soon your online life might become more developed than your real life.
Virtual worlds foster creativity because you can see what other people have created and become inspired, or discover a world that brings out talents you did not know you had.
I think the future of virtual worlds will be people getting together in person and online, putting on VR visors and playing games like escape the room, working on projects, and just hanging out.