The difference is that in your later two examples, a business lost something, their time / labor. If you took someones seat at the theater, there will be a disruption at the least, maybe the customer does not get their seat or you have to be kicked out or cleaned up after, but if you don't disrupt anything or make a mess, you caused no harm whatsoever.

No one looses anything when someone copies a file without permission. The FBI and other propaganda sources would have you believe that media companies would make more money if you didn't copy the file, there is no evidence of that, only evidence to the contrary, even so, if it were true, taking an action that causes someone to earn less money than if the action were not taken is not theft. If I open up a store, next to your store, and sell the kind of products you sell, you will make less money than if i don't, but no person with any self respect would ever claim that I stole anything from you, except you, the angry store owner. The reality is that these laws and their associated propaganda exist because the wealthy ruling class is terrified of making slightly less money for their investors.

Think back to the moment you learned that copying was considered theft, you knew it was ridiculous at the time, but you've seen so many FBI warnings, and so much of your favorite youtubers whining about facebook videos that belong to them with more views than theirs, steeling their precious views, even though almost no one on earth watches videos on facebook and on youtube, and no one who knows and wants to support a creator would ever watch their content in a way that would instead support someone else who provided no new value. The reality is that the youtuber was never going to get any views from the audience of the facebook video if the facebook video didn't exist, but because it did, many people followed the comment saying that the video was stolen right back to the original creator. Likewise the people who are pirating software or media are probably not going to buy it in any timeline, but now that they copied the content, they might promote it to people who will actually buy it, people who otherwise would not know about it.