Why does this happen? "Murphy's Law"

Why does this happen?

You are in a store, simply browsing and want to be left alone when infinite clerks flock to you and ask “May I help you?” while OTOH, when you actually need assistance, no clerks are to be found?

The same goes for restaurant servers. You are discussing something very personal with your company when the server keeps coming back, “Is everything okay? Can I get you anything?” blah blah blah Go away already, I’m trying to have a conversation here! Ugh!

and finally,
Why does everything you want to buy, go on sale, when you have not the money available to spend on it? When do you have the money, it’s not on sale or out of stock. And worst of all, you spend your money on something, and within a weeks time, it goes on sale after you paid full price? Arrrgh!

:::vanes bulging, shirt ripping, pupils dialating, flesh turning green, Incredible Hulk emerging:::