I am surprised by it because in my family we usually buy only things we really need, I am starting to understand how other people's spending habits can affect the business.
Do you also find yourself spending more on you payday?, or you approach your expenses differently?
My case is different because I have streams of income, and I don't depend on a monthly salary. Also, your family may not be relying on the payday which is why it might not be obvious to you. Those whom you are referring to are paid job employees, there might have been a long list of what they need, which could be a pressing one or needed for the whole month. It happens everywhere, not only in your country, there are needs and wants every time, but to them, money is a constraint which is being solved when they receive their monthly salaries.
For those who are business people or are financially free and not depending on the monthly salary, you would never know their spending culture because they get what they want when they want it. Even if they spend more on frivolities than those who depend on their payday, you will definitely not know because there wasn't a time limit for their financial freedom.
Payday or should I say payment week is also the week that ATMs are mostly busy and debt paid in my country. It's also the time that sellers claim they record the most sales, which I believe is normal and for obvious reasons.