Historically, private was file-scoped, but was changed in SE-0025 to be declaration-scoped. This led to the introduction of fileprivate as a file-scoped access level.
The core team later considered that a mistake, although it was also impractical to undo ("is in use within the Swift community and in established patterns, such that it would be harmful to remove the functionality"). There was an idea to rename the keywords, but it was considered too much churn. Thus SE-0159, which would have reverted SE-0025, was rejected.
Sometimes people get confused and think that fileprivate itself is somehow discouraged. AFAICT there was never any significant dissatisfaction with the concept of fileprivate - it's with the spelling; some would like it to be the "default private".