The sense of responsibility. I work online as a customer support rep from home. I've worked for this company for over 8 years and previous to that had my own online business.
When I worked for myself, I could push things off and just think "hey I can get that later". Sleep in a little, do some other distracting activity.
Working for the company that I do now, I know what is expected of me. I know that the company is based out of the west coast area and I'm in the midwest and that they need me to be online very early in the morning to deal with overseas and East coast customers. There's a sense of doing the job and doing it right. I also get paid very well for what I do and I realize that. I can't think of another job that I could do from home, in my PJs or even out in the real world, where I could make the money I do. So in return for this luxury of working from home, I do my job, do it well, do it on time, and I actually do love it.
So while I technically don't leave the house for someone else. I do get up and get myself online & begin work at 5am each morning as I should.