In Canada, why do we get those GST or HST Tax Credit Cheques?

Im curious why the Government sends us those Tax Credit Cheques. If the amount you recieve from those cheques surpes the extra amount we pay on our daily expenses due to Sales Tax, then whats the point in paying Sales Tax in the 1st place???? Same thing if it is the other way around, if the extra amount of money you pay on your daily purchases surpes the amount you recieve from those cheques.