So, I think there is an important clarification that needs to be made about aspect ratios and movies.
First, home exhibition and the 4:3 aspect ratio never influenced movie production and exhibition. These technologies arrived long after the current (and past) standards had been established. And with that, a bit of history:
Background:
Film production aspect ratios have varied somewhat over time. One of the earliest of these was known as the Academy ratio, named after the Academy of Motion Picture Arts and Sciences and established as the standard in 1932. Prior to this, silent films had been filmed at a 4:3 aspect ratio, long before that ratio was in use in modern technologies. The reason for the change when audio was added is that the soundtrack occupied space on the film where the picture used to go, and having a taller picture proved to be disorienting and technically-challenging.
A number of aspect ratios were used for widescreen format going into the 1950s-60s. The obvious issue with these formats is that all, to a greater or lesser extent, wasted a good chunk of the actual film, leaving a significant amount of unused space between frames with 4 perforations per frame.
Thus, at about the same time as the Academy was standardizing the original widescreen format, anamorphic technology started to come into use. 896
This compresses the image horizontally such that more of the film can be used. Then, on the projection side, special lenses are used to re-stretch the image back to it's original width. The most widely-known of these, Cinemascope and Panavision both came into play in the 1950s and are still in use today. The standard exhibition aspect ratio for an anamorphic film is 2.39:1.
Film vs. Home Formats:
Back when most TVs were of the 4:3 variety, a movie filmed in anamorphic 2.39:1 aspect ratio would lose nearly half of the picture if cropped to this ratio; hence letterboxing was also widely used to avoid this loss.
Even today, with a 16:9 display, the standard cinema exhibition aspect ratios "flat" (1.85:1) and "scope" (2.39:1) are wider than the 16:9 ratio and will result in letterboxing. It is now common to have settings on your TV, however, to control the zoom/crop level, with the media itself presenting the original theatrical version of the material.
Additionally, many theaters don't have screens that are perfectly 1.85:1 or 2.39:1, but instead fall somewhere in the middle. For these theaters, cropping is a reality - it is quite common to crop the top and bottom of a 1.85 feature, or the sides for a 2.39 feature so that it will fit the full-height or full-width of the cinema's screen. Because of this, safe zone areas have been established and standardized such that cropping can be done safely to a reasonable extent. 896