Although the Date and Date/Time fields have the option to set a default of 'Current Date plus # days' this defaults the time to 12:00 AM for Date/Time fields and Time fields don't have a default option at all.
However, ideally we should have multiple options to default the time in Date/Time fields and Time fields. Some suggestions are;
1. Current time
2. Current time plus/minus # minutes
3. Start of Next hour/half hour/quarter hour
I agree completely. It would also be nice to have a setting on the time to allow a range to be specified so you don't have to write code to limit the times selected to be during normal business hours.