Why the default transaction level for MSSQL is different that other databases?

fun getDefaultIsolationLevel(db: Database): Int =
            when (db.vendor) {
                SQLiteDialect.dialectName -> Connection.TRANSACTION_SERIALIZABLE
                OracleDialect.dialectName -> Connection.TRANSACTION_READ_COMMITTED
                PostgreSQLDialect.dialectName -> Connection.TRANSACTION_READ_COMMITTED
                PostgreSQLNGDialect.dialectName -> Connection.TRANSACTION_READ_COMMITTED
                else -> DEFAULT_ISOLATION_LEVEL
            }

const val DEFAULT_ISOLATION_LEVEL = Connection.TRANSACTION_REPEATABLE_READ