Actually we do log stats on an hourly basis. It just seems like we don’t because the stats reports only show daily stats.
We added hourly stats recording a few years ago when we added time zone support. You can change your time zone and all of your stats will shift retroactively. This works because stats are stored with UTC time down to the hour and we apply the time zone offset in the reporting script, not during the recording.
There is one place where we do expose hourly stats: the toolbar sparkline. This is a very small chart that shows 48 hours of views in the toolbar at the top of WordPress.com and Jetpack blogs. If you’re running Jetpack you may have to check your stats settings via the Jetpack admin page in your wp-admin; the sparkline is optional there.