There are not enough hours in the day! Have you noticed this? I surely have! With a full time job and a 40min commute one way I find I don't have enough time for my crafts. Solution: crafting while commuting. As mentioned before, it helps pass the time, but also it's a great way to utilize the time that would otherwise be wasted.
It is also a great way to promote your work. People are often curious to know what it is that I'm making and this provides me a great opportunity to advertise my blog or Etsy shop. A little business card is always helpful to have on hand when crafting in public. You never know when somebody grabs your knit-work in awe and demands to know where can they get one!