When you are creating videos or other content the files can become quite large. Email services have a limitation on the size of attachments (usually 15-20MB although SMA allows 25MB). Schoology also has maximum file sizes that it will allow depending on what is being uploaded (100MB or 528MB).
So when you want to share a large file(s) with someone the best method is to use your Microsoft OneDrive App/Account. Place the file or folder there and then you can share it with other students or teachers.