Sharon Hayes clearly explains why she does not work for free in 7 Reasons Why I Can’t Do “Free”, check it out.
3. It Zaps My Creative Juice
Each of us has only so many truly productive hours in a day. In my own case, I can get in about 5 solid productive hours on a typical day. It’s like a bank for me. Each day, I start off with this reserve of 5 hours. As I do work through the day, the reserve gets depleted. But it gets depleted at a faster rate when I have to shift gears more frequently.
6. It Doesn’t Stop at One Request
I used to be much more generous with my time – that is until I got to the point where it was detrimental to my own life and well-being. One of the things I discovered is that a significant percentage of the time when I helped someone out for free, they would come back – often repeatedly – for more free help. It has to end somewhere.
I totally agree.