Dressing Rooms Left, Enter Right

[MarkBearSF]

Today's chapter of things you come up with at 3 AM if unable to sleep...

It occurred to me that in practically all of the movies with stage scenes, and my personal experience with older theaters, the dressing rooms and offices tended to be on the house right/stage left of the theater. Yet, I believe one of the truisms in stage design is to favor stage right for actions, and when I think of shows I've seen, it DOES seem that major set pieces with doors and entrances tend to be stage right (house left). 
 - Are my recollections generally true?
 - Is there a logistical or stage-logical reason for this?
 - If there's no good reason, do more modern theaters have dressing rooms on the other side?

[AEA AGMA SM]

I've worked in theatres of varying ages all across the country and there is no rhyme or reason as to where the dressing rooms are placed. Some will even have dressing rooms on both sides of the stage. I assume it all has to do with the layout of the rest of the building and the way the building is situated on the plot of land it's on.

[Tag]

Yes dressing rooms are found in all sorts of arrangements and do not generally favour stage left.  

The favouring of stage right for major actions can be traced to a Western audience's connection with reading from left to right.  It's a natural (or learned!) reaction to connect with the left first.

[MarkBearSF]

Thanks.

Of course they'll shoehorn any backstage spaces wherever they can fit 'em. My experiences backstage, primarily at old SF houses like the Curran and Geary, were oriented to the right side of the house - but because I didn't see stuff on the other side doesn't mean it doesn't exist. And like the western stage connection to stage right, I'm sure there's a filmic analogue which favors having the footlights and audience to the left of the screen - thus, backstage on stage left. 

Like I said, 3 AM.