In the world of programmer, we're taught to use "best practices" when building applications.
As in life, we're also taught to do the same. For example, it would be considered best practice to drive the speed limit when transporting oneself in a vehicle. And if you drive any road anywhere, if you drive the speed limit chances are you'll be pushed off the road by speeding aggressive drivers.
Same with diets, its considered best practice to follow 3 balanced meals per day, containing the 4 basic food groups. And if you pass any fast food joint anywhere, people are lined up for miles eager to eat some kind of processed meat, congealed wax known as French fries and some carbonated beverage which will strip the paint off your car.
How about budgets, it's considered best practice to have a budget in place to account for your household spending, so you don't spend more than you earn. And if you go to any Mall anywhere, you'll see people buying the latest fad name brand items, financed on credit card at 18%, always paying the minimum payment each month and juggling several credit cards.
And sleep, it's recommended people to sleep an average 8 to 9 hours per night, and if you see people are on the computer, television, bars until the wee hours of the night and survive on 4 to 5 hours on average.
So as you can see, best practices are recommended in just about every facet of human life. And some people choose to follow them, however the majority throw caution to the wind and completely disregard.
So now you see human behavior, don't be surprised the next application you inherit, the person did not follow "best practices".
And there you have it!