For some reason, FormattedValues are not returned for dates and currencies and decimals. This is particularly important for dates, as the FormattedValue will contain the date/time in the calling user's timezone. The PowerBI online servers are all set to UTC, so it is difficult to get date/times in local time without the FormattedValue of date/datetimes. Note this is important for "date only" types as well because they are set to midnight, so the FormattedValue is still important for "date only" types.
For some reason, FormattedValues are not returned for dates and currencies and decimals. This is particularly important for dates, as the FormattedValue will contain the date/time in the calling user's timezone. The PowerBI online servers are all set to UTC, so it is difficult to get date/times in local time without the FormattedValue of date/datetimes. Note this is important for "date only" types as well because they are set to midnight, so the FormattedValue is still important for "date only" types.