A67-A67 (experienced mapper!) Reverted (highway=service) to (highway=residential): "Fix tagging ventwegen".
This Changeset was, again, Reverted to (highway=service).

OSM Wiki also has a view on this issue:

https://wiki.openstreetmap.org/wiki/Tag:highway%3Dservice 
"Generally for access to a building, service station, beach, campsite, industrial estate, business park, etc. This is also commonly used for access to parking, driveways, and alleys".
"This is not a tag for frontage road, sometimes called a service road. That should be tagged depending on what function the frontage road serves".

https://wiki.openstreetmap.org/wiki/Frontage_road
"A frontage road (also access road, service road, parallel road, etc.) is a minor road running parallel to a higher-speed more major road, often in an urban setting. The frontage road is connected at some points with the major road. A frontage road is frequently used to provide access to private driveways, shops, houses, industries or farms. Functionally, they usually behave as collector roads for local traffic along the sides of the highway. A frontage road is often, but not always, a one-way road.
Do not use the highway=*_link tag for the frontage road. Simply use one of the normal highway=* tags. As the frontage road is less important than the major road, it must also have a lower highway=* tag than the major road – regularly highway=residential. Example: If the major road is "tertiary", then the frontage road is neither "tertiary" nor "tertiary_link". It has a lower type: can be "unclassified", "residential"…"

Many highways that are less important than (highway=unclassified/residential) have been updated from (highway=unclassified/residential) to (highway=service).
Sometimes correct, sometimes not "best option", sometimes "error" or even "complete and utter nonsense".

Renderers don't like (highway=service) on a through route.
OpenFietsMap f.i. will revert ALL (highway=service) to (highway=unclassified) if bicycleroute=yes.