"Theater" vs. "Theatre" in American English

Britishisms often creep into American English as personal affectations, or because the British spelling is perceived as being more "upscale." In my experience, the "theatre" spelling largely appears in two contexts in AmE: in the names of theaters (dramatic or cinema) that wish to project an upscale vibe, and in writing by devotees of the dramatic arts, who as a group can be a bit... well, "pretentious" is such an ugly word, but there you have it.

We don't exactly have shortages of either theater geeks or social climbing movie houses in the US, so that's probably why the "theatre" spelling seems so common.

Here's a relevant Google Books ngram (click to embiggen and interactivate):

Facts to glean here:

• For most of the 19th century, "theatre" was pretty much the only spelling used on either side of the Atlantic.
• "Theater" started out small throughout the second half of the 19th century in American usage with almost no usage at all in Britain.
• In American usage, "theatre" stayed fairly flat throughout the 20th century, while "theater" usage grew quite a bit. "Theater" only surpassed "theatre" in American usage sometime in the late 1970s.
• Since the 1980s, "theatre" has been on the decline in American usage.
• "theater" has been rising in British usage throughout the twentieth century, but usage is still primarily "theatre"