A sentence should contain a complete thought. Once you finish your thought, you can finish your sentence, usually with a period. That makes your sentence more readable too. Yes, it’s legal in English to use conjunctions to put several thoughts into one sentence. But it takes a special kind of mind to follow the train of thought in a sentence that has two or three thoughts.
Maybe some writers don’t know when their thought ended, so they don’t know when to put the period. They go on and on and make more and more statements and even change the subject, but they don’t ever put the sentence to rest and keep on going and going.
Technically speaking, to understand a complex sentence, the reader has to parse or diagram the sentence in his or her head. Okay, suppose I’m reading a sentence in Rolling Stone. Was that sentence talking about actors, and what are the actors doing anyway, and what the subject of the sentence, and what is the subject doing, and does that word shot mean that somebody got shot or somebody took a shot, and does it refer to the policeman or the actor or the photographer?
Pretty confusing, isn’t it? So make your sentences simple. Put a period at the end of the thought and leave it there.