It is simple. It's human nature.
For Lying- To get out of something that they don't want to deal with, or to avoid trouble. Note: This usually leads to MORE trouble.
For Cheating- Low self Esteem, usaully don't think they have a chance in winning. Low self Esteem for both cheating in a bed, and in a game.
Stealing- To gain something immediately that they don't think would be worthwhile working towards. They think why bother working for it when i can have it now.
Has some1 done this 2 u lately?
It's not fun on the receiving end...