Probably many underestimate the importance of the sound.

A home theater arguably is as much about the subwoofer and surround speakers as it is about the screen.

Especially the subwoofer has a big impact. When you feel the sound it's literally impactful. At other times, it really helps immerse yourself in the scene, even if it's not a typical bass sound, but like background noise in a busy city street.

The properly configured subwoofer makes you feel like you're there, while it just falls flat on a regular speaker.

That said, the fewest people have a home theater setup, so it's probably irrelevant to why people stopped going to the cinema.