This is some kind od devops busywork? Say you are developing a app and you change the database 20 times: you write 20 migrations because every table and column name is cloned into variables and models in an infinite amount of places. Careful thought must go into these changes. If you are rolling back migrations in production you are in your own personal hell.
Deleting old schema migrations is just busywork.
It doesn't hurt if they are there. Disk space isn't a problem, and they still take up space in git repo anyway.