Why are date and time stored in separate fields?

In Vantage 8, date and time is stored in separate fields although in
SQL Server, you can store both in a single field. It's not a problem
for me but I'm curious to know why it's done this way. Does anyone know
what's behind this design?

FYI, to support custom Crystal reports, we created views to mirror each
table and combined the date and time into one field using the SQL
Server DateAdd() function. The result is a readable date/time.

We also gave meaningful names to all the generic 'description'
and 'name' fields so you can join two views without having to alias
the 'name' field in your select statement because it's already done in
the view. This has been very handy.

Brad