Usually people used cascade delete when a column of one table was reference by other tables (foreign key).

For example Table A has column1 unique not null. Table B has column1 foreign key to table A column1. When someone deleted the row that had column1 in Table A, then the cascade delete would delete all rows that contained column1 in Table B to maintain the referential integrity.

Yes it is dangerous. You would end up delete a lot of rows in other tables that you did not know.