If you're using programs and SFDC campaign code syncing, you're probably not going to need to use the "Sync to SFDC" flowstep in many situations. I recall using it more back when programs didn't exist and I wanted more granular control over when stuff synced over. More recently, at my previous organization, we did use the flowstep in a few isolated circumstances when we wanted to ensure leads who had accumulated a certain lead score, even if they didn't accumulate it through a specific program progression, would still be caught and dumped into SFDC.
That said, I'm sure others have more creative uses for it.
Hope this insight helps!