I've done both – in my undergrad I staffed a drop-in help night for a required freshman comp class, and later on in grad school I made extra cash proctoring a "alternate testing center" for students needing retakes and ADA accommodations. I can see the comparison to drop-in homework help centers. But as a test proctor my job was to get out of the way of students as much as possible while keeping things quiet – I'm not sure it's worth idealizing as "caring".