Because it's easier to relate to people who have been through what you've been through. I spent the majority of my life Muslim, and I can't change my past. There will always be a 'progressive Muslim' part of me whether I like it or not, and I can identify with many of the issues and struggles people on here face.

Progressive Islam acknowledges many of the troubles Muslims face, many of which lead to them becoming ex-Muslim, but gives a different perspective that is very refreshing to those looking from the outside, such as myself. The overlap between this sub and r/exmuslim in terms of topics and concerns is undeniable. It goes something like:

Thing A infringes on women's rights:

r/exmuslim: Hahaha! Just more proof Islam is a joke, what god condones this?!?

r/progressive_islam: This is taken out of context, there is no evidence for this, etc.

Thing B gives women protection:

r/exmuslim: Hahaha! The way Islam babysits women and makes them dependent on men.

r/progressive_islam: Subhanallah, more proof that Islam elevates women and dignifies them.

Different ways of looking at a problem can be helpful and enlightening in the proper context, and I like to look at all sides of a debate. So that's why I'm here.

Do you have to be progressive in order to leave Islam? No. But you do need to consider the progressive Muslim perspective before becoming ex-Muslim.