In my case, I was unhappy with the ongoing BFing problems and the stress/anxiety/guilt and everything else it was causing me, but was also unhappy and very upset at the thought of giving up! I felt stuck on a BF/top up/express roundabout with no end in sight and out of control (DD had a TT recently fixed but no quick improvement). It felt like a lose-lose situation at the time. I wanted 'permission' to stop because the situation was making me unhappy and I was getting pnd, although of course I wanted to keep going on because breastfeeding was what I wanted, and we had struggled on for 8 weeks, I didn't want it to go to waste.
In the end I stopped BFing as much and went to only twice a day BFing followed by topping up and bottles the rest of the time, with no expressing. I managed to give my DD breastmilk until just over 7 months. She is now 8 months and she weaned herself a few weeks ago.
I thought 'happy mum, happy baby' rather than 'happy baby, happy mum' because while she seemed happy, I definitely wasn't! I thought that if I struggled in the situation we were in it could rub off on her. If I was happier, I could spend more time with her rather than stuck on the pump feeling disconnected, which in turn would make a happy baby too.
We absolutely need to offer more mums support, whatever their choices. But like toddlerwrangler said, sometimes we do want to hear that it's ok to give a bottle too! Mixed feeding isn't always discussed as an option. I felt it had to be either/or.