I mean this tax regulation seems uneven and it seems that people who have to pay taxes are people who deal with large amounts of money. Let's say a farmer in 1 harvest (3-4 month) earns $2000, he will remain tax free if not registered or he doesn't register it whereas an employee from the start is already registered with the taxpayer even though their monthly salary is $300. What do you think? I'm a little confused with this tax rule.
Indeed, sometimes the tax regulations are complicated and sometimes they seem unbalanced. In general, taxes are designed progressively, meaning those who earn more pay a higher percentage of taxes. In the case of the farmer you mentioned, if they made $2,000 in the crop, they probably wouldn't have to pay taxes if they weren't registered or didn't report their income. Again, if their income exceeds a certain threshold, they may be required to pay taxes.
I think the purpose of taxation is to provide revenue for the government to fund public goods and services, and to ensure that everyone pays their fair share based on their ability to pay.