Yes I don't feel like that every person have based knowledge of DBMS....It only applicable who working on that part like if somebody only interested in front end work then that person should know at least basics knowledge about the backend database(DBMS)
yes, if some person is working on projects which has database, that person should have base knowledge on DBMS main reason why we use DBMS over the file system is: 1.relationships among data 2. security 3.reliable