Our brain is built in a way that it can concentrate on one thing at a time. So when trying to learn to handle a manual gearbox and learn to navigate in a traffic communication system, then it's going to take a lot of time.

It's much easier and therefor quicker and cheaper to learn with an automatic gearbox car. 

If you really need to then you can always learn to handle the manual gearbox any time you want (before the exams or when you already have a driving licence. In this case you will only spend one or few lesson on manual gearbox.