SAG-AFTRA Writer's Strike: Why is it happening?

Unless you have been living under a rock, you have no doubt heard about the SAG-AFTRA strike, but what is it all about? 
Currently members of the Writer's Guild of America are on strike for being underpaid by major production companies that are pulling in millions every year thanks to their hard work. They attempted to negotiate for better pay but when a deal couldn't be met, they went on strike. They were later joined by the Screen Actors Guild in a show of support and to try and negotiate for residual payments from streaming sites. 
During this time, actors and writers will not work or cross the picket lines to promote any current movies as a show of solidarity. 
Another major issue they are fighting against is the use of AI in both writing and when it comes to background actors. The people in charge of the production companies want to replace writers with AI and use AI software to capture the image of an actor that they can then use forever, while the actor only recieves a one off payment of just a few hundred dollars. Many actors get their start in the industry as background actors, so this will push them out of the industry.
Despite public opinion, most writers and a lot of actors do not receive millions for their work. While there are A listers who may get paid more, that is not consistent with every movie, and their co-stars are paid much less. For example, in 1994, Jim Carrey was an A list actor and he received $7 million dollars for his role in Dumb & Dumber. His co-star Jeff Daniels received only $50,000. They are both the stars of the film and it would be impossible to make the film without both of them, yet the studios clearly view things differently. Admittedly, $50,000 might be more than some of us see in a year, but when you consider that they are relying on a movie being popular to get more work, which they can't know in advance, and the time between filming and the movie coming out, which can be years at times, then that $50,000 probably won't last very long. 
Regardless if you think actors are overpaid or not, they have done the work and they deserve to be compensated. How many of them have starred in your favorite shows or movies? 
Writers recieve much less for their work and are seriously undervalued. Many are not hitting the threshold to receive health insurance. So until an agreement is reached, they will continue to strike and shows and movies will be delayed. 
When you consider that the money they are asking for is less than 1% of the studio's profit, you can see how greed is driving the studio execs' decision. 
Hopefully, a fair agreement can be made and they can return to work soon.