I see. There are specific guidelines for Connecticut, although I don't necessarily agree with them:
https://wiki.openstreetmap.org/wiki/Connecticut/Highway_classification
Previously I was going by the wiki page for highway=unclassified:
https://wiki.openstreetmap.org/wiki/Tag:highway%3Dunclassified
which says "Residential roads, primarily for access to properties, should be tagged highway=residential instead". Obviously the road has a number of residences along it, although it's hard to say whether it's primarily used by residents or through traffic. I think the Connecticut default has been to tag/leave them as highway=residential. Minor roads without residences are quite rare here (unlike the UK), although at the same time they aren't exactly dense and suburban, so I see your point.