When to use prepared stmts and ordinary stmt & can we get rid of the use of ordinary stmts

Can we dispense with or get rid of ordinary statements and always use prepared ones?!.. People say prepared statements are better and protect from SQL injection, it also specifies the type of data has to be inserted using bind and many more.. , but I've not found anyone to say Always use prepared statements and do not use the manual method so if that is right declare it to me and if it is not declare the differences!