To avoid hussle with customers - from different countries - that would be a little but nice thing.
To handle .csv files, Microsoft Excel uses the List separator defined in Windows Regional settings.
In North America and some other countries, the default list separator is a comma, so you get CSV comma delimited.
In European countries, a comma is reserved for the decimal symbol, and the list separator is generally set to semicolon. That is why the result is CSV semicolon delimited.