How is it protecting any 'lobby'? There are many free options. I've been filing taxes since I was 15 without the help of an accountant.
The government would love to just take the money out anyway, it would mean the average person would pay no deductions and have more taken out without them even knowing.
It's better to have some friction when it comes to taxes, so the population has an idea of what's being given to the government every year.
When it's invisible, like in your country, citizens don't actually know what they're paying and the government can just spend it with no accountability.
A similar example of this is the gas tax. It's not separated out and the government continues to raise it and blame the oil companies for the increase in cost.