This is just because Apple devices do not have the ability to import CSV files. A similar situation occurs with iOS, which needs the vCard (VCF) format. Even iCloud does not allow direct uploading of a CSV file. I also thought that iCloud would convert the file for me, but in fact, it only accepts VCF. So the only way out is to
convert CSV to VCF first. Once you have downloaded the VCF file to iCloud, it will be linked to your iPhone automatically. Also a CSV to vCard converter makes sure that the vCard file is compatible with iOS. One time, when I was using
GainTools, it produced a VCF that could be easily merged with iCloud without any trouble. So, first, change CSV into VCF, and then import the file. That is the only method that works consistently for Apple devices.