When Claire Wixted went to see “I, Tonya” in February, she felt like she was the one on display. A 27-year-old working in media advertising, she had decided to go to the movies alone for the first time, and was worried other moviegoers were watching as she picked out a single seat.

“Are they judging me like some dateless freak?” Ms. Wixted thought. “Do they know that I made this choice voluntarily?”

A...