This feature has been labeled as deprecated. The recommended replacement is: barrier=kerb.|
The reason is documented in Deprecated features. You are still free to continue to use or interpret this tag as you see fit since OpenStreetMap does not have “banned features”. Under no circumstances should you (semi-)automatically change “deprecated” tags to something else in the database on a large scale without conforming to the Automated Edits code of conduct. Each of these changes would be reverted.
Curb is the American English spelling for kerb. Please use the British English spelling in OSM. If you find tagging as curb, please verify it is indeed a barrier for vehicles and wheelchair drivers, as shown below, and change the tag to barrier=kerb.