The goal of Analytics is to show real trends across business days and not show lines that dip to zero constantly. With this in mind, majority of data will not show weekends, unless specifically requested. 

All totals, such as Completed Steps, Total Activities, etc. include weekend data when the selected data range includes a weekend.

All line charts EXCLUDE weekends (Saturdays and Sundays) in their charts by default, unless you select a date range of less than 5 days which includes a weekend.