Haider, people refer to income in 'per annum' basis in almost all western countries. Nobody talks about 'monthly incomes'. Whenever someone mentions an income amount, it is assumed to be an annual one.
As for the tax system, its called a 'progressive' tax system where the more you earn, the more you pay.
At first the tax may seem overburdening, but keep in mind there are a lot of tax credits you can avail at the time of filing a tax return after completing a year or part-year of residency in Canada.
People who make the excuse of living 'hand-to-mouth' do so because they don't keep their expenses in check. They pay a high rate of insurance on their car, they have financed or leased their cars and make payments on them, they tend to shop the latest gadgets and dine out frequently, they buy their furniture on credit...then they phone back home and tell their relatives how they're living 'hand to mouth'.
I earn 12% less than $40,000 annum before taxes and deductions, and I don't live hand to mouth. I support my siblings, myself and my parents. I go out to eat and visit the US from time to time. I enjoy dining out, going to concerts of my favourite bands, travelling to spots and cross the border. What I don't do is shop for unnecessary luxuries or drive a car. What I do is live in a cheaper area and use transit.
$40,000/annum is not hand to mouth. Anyone saying anything differently has no idea how to budget their income and make the most out of their money. However, most white collar jobs in Canada are kind of underpaid whilst blue collar jobs are overpaid. They like to maintain equality of income here, its not a capitalist economy like the USA.