One can be a cultural Muslim. They even wear hijab, pray sometimes and fast. But deep down they don’t know how to believe and can’t believe. Yes, I agree they will miss being a believer. It is lonely and a harsh world for them.
I don't want to say anything heretical but... I think in a way, a person can never really entirely leave Islam. Don't get me wrong- if someone is a kaffir, they're a kaffir, I'm not denying that they're outside the fold of Islam.
But what I mean is... on some level deep down- Islam is built into your fitrah. If a fish bites a hook- you can get the hook out of the fish- but we cannot get rid of the fitrah that is built into human beings. Islam is innate. You are drawn to it even if you live in some culture where you've never heard of Islam. As long as you follow Islam- you are following your own innate human nature. Your own innate human nature tells you that zina is wrong, that God exists and that He alone is worthy of worship. There is nothing in the world like Islam. People talk about freedom- I believe Islam is the ultimate pinnacle of freedom as far as we humans are concerned. I believe it is the highest form of freedom. It represents the freedom to be in harmony with your deepest, innermost human nature.
The more an ideology goes against Islam- the more it requires its followers to go against their own nature. I think this is oppression. You can't just follow what's innate. An ex-Muslim continually has to fight a war against their own inner nature. Of course they cannot stop obsessing about Islam and of course they constantly want reassurance that they're right because they know deep down that they're wrong. They want others to join them so they can have relief from their insecurity.