Hi,
The reason for this is the innate weakness of people who succumb to temptations easily. It is a part of human nature to sin, to listen to Satan more than trying to listen to God. It is easier to do bad things than to do good things. A lot of times doing the bad things are a lot more fun than doing what is right. It is always a daily struggle to be on the right track. Just like eating. It always feels good to eat the sweets, cakes, or anything unhealthy for us than to eat salads, low fat foods. People find these good food unappealing and boring, so you see more obese people than lean healthy looking people.