It's extremely easy to validate in automatic way that only proper call's are used to call the sprocs also if you limit web app db user to only have permission t

It's extremely easy to validate in automatic way that only proper call's are used to call the sprocs also if you limit web app db user to only have permission to execute appropriate stored procedures you mitigate a good number of attacks even if someone did call the sproc in unsafe manner that allows sql injection now the attacker needs to guess sproc names and signatures and still limited in what he/she can do. This assumes that sprocs are themselves not written to concat sql and then execute it :)