Maybe we purge because we find ourselves in the wrong situation to take our dressing/transition to the next level. When I was younger and I purged it was usually because something made me feel guilty about dressing in private as the real me. Possibly I heard a person of authority talking about how men dressing in women’s clothing were perverted. Or possibly because a significant other came to close to finding my cache of female clothing.
Gender dysphoria became so strong at the age of 60 that I was forced to come out to my family for the sake of my sanity. After that I chose to never purge again.