Because the regular movie bore me. I am too over critical. I will see faults in stupid movie plot lines. But with period movies, usually its real life portrayed in a dramatic fashion. I get to enjoy history, costume, and a good story without being critical about it. Yeah, i could be critical about the acting, or the mistakes in historical depictions since i am a fan of History but that is minuscule. I appreciate them making a period movie. It is very expensive and taking time to do it is worth it.
As to the documentaries, oohhh babyyyyyyyyyyy those English professors give me mental orgasms ! !