Of course you can do that manually specifying start/end time repeats etc on each event, which depending on the number of layouts, displays ie over number of events that need to be created may take some time.
With dayparts you create a daypart that has pre-defined start/end (and may have additional configuration as well ie exceptions) and use that in your events.
All of that is possible with custom scheduling as well, but with more hassle, you’re not forced to create or use any dayparts in 1.8 series if you do not want to.