I know people who do this, including my mother. I think it comes from wanting to be helpful, needed, and wanted.

I catch myself agreeing to do favors and then regretting it. I feel a sense of obligation to say yes even when I want to say no... or I might say yes because the moment the request is made, I am thinking about wanting to help, but when reality sets in and I realize how much time/effort is involved when I already have sixty million things to do... I have regret. Stopping the immediate instinctive yes is something I've been working on for a few years and it thankfully happens less often now.