The reason for the approximately 50 character limit is because there’s many tools that display a single line and will truncate it if it’s more than about that length (though really the point of truncation can vary wildly – plenty of tools will let you go twice that before they cut you off). So if your one line summary is too long, it’ll be cut off and harder to understand your commit at a glance.
You always can elaborate in a second paragraph, at any rate.