Is there a need for Sophos Scheduled Scan on End Points ..??

We are finding it difficult to catch all of our End Points in a scheduled scan. I have tried to adjust the times based on peoples shift, and create daily scans to try to scan those end points that still show as "never scanned". 

We have also seen an increase in performance related issues with Macs when the scan kicks in. 

the question I have today and trying to gauge what industry peers are doing, is if we have Real Time Scanning turned on and scanning everything in real time,  it necessary to have scheduled scans turned on too? If some machines are not being scanned anyway, is there anything to gain by having scheduled scans turned on at all.