Debe hacer una combinación externa con una tabla que contenga una fila para cada mes. Suponiendo que no tenga una tabla de este tipo, puede crearla sobre la marcha con una consulta UNION codificada:
SELECT * FROM
(SELECT DATE_FORMAT(now(), "%b") as Month
UNION
SELECT DATE_FORMAT(now() - INTERVAL 1 MONTH), "%b")
UNION
SELECT DATE_FORMAT(now() - INTERVAL 2 MONTH), "%b")
UNION
...
SELECT DATE_FORMAT(now() - INTERVAL 11 MONTH), "%b")) AS Months
LEFT JOIN (SELECT DATE_FORMAT(drives.timestamp, "%b") AS Month,
drives.timestamp,
DATE_FORMAT(drives.timestamp, "%d-%m-%Y %H:%i:%s") AS Exact_date,
drives.departure,
drives.destination,
drives.route,
CONCAT(drivers.name, " ", drivers.surname) as driver,
drivers.id as driver_id
FROM drives, drivers WHERE drives.driver = drivers.id
AND drives.timestamp > DATE_SUB(now(), INTERVAL 12 MONTH)) data
ON Months.Month = data.Month
ORDER BY data.timestamp
Cualquier mes sin registros tendrá una fila con NULL
en las columnas de datos.