Because attempting murder on your boss wasn't enough the first time.
Dale (Charlie Day), Nick (Jason Bateman) and Kurt (Jason Sudekis) are back with another round of misadventures. When the friends are trying to start up their own business, they soon get screwed over by a wealthy, con-artist business man (Cristoph Waltz) who cancels the order they created and steals their idea of the invention they made called the Shower Buddy. Going back to old ways, they plan to kidnap his son Rex (Chris Pine) for ransom money to help save their business.
Horrible Bosses was a fun time, not as great as the first one, so it's a typical not-as-effective-sequel because nothing new was brought to the table. Except new jokes, which is one of the main reasons I enjoyed Horrible Bosses 2. Again, not as hilarious as the first one, the film still has me cracking up during several scenes of the movie. Familiar faces were spread all throughout the film which was great to see, such as Jamie Foxx as Dean Motherfucker Jones and Jennifer Aniston as the sex crazed, Dr. Julia Harris, but the new ones were the ones that surprised me the most. Mainly, Pine's character, Rex. It was weird to see him in a new light as a hilarious and somewhat psychotic Daddy's boy. Both he and Foxx had the best lines and scenes in the movie, so I will give the film it's credit for that.
However, it loses some of the integrity and intelligence of the first film because the three leads somehow turn into huge idiots. Nick, still being the smarter of the three is still smart, but does idiotic things just like his two friends. It's a carbon copy of the first film with dumber leads. So, if you liked the first one, you'll like this one as well. If you haven't seen the first one, I'd highly recommend it or maybe just this one since they're just about the same.