Well, I can't answer for GP but I can relate to both of you, because I swing back and forth between the two modes.
I was also raised religious (Hareidi) and am now entirely secular, by most counts. And I've spent many hours trying to argue that it's ridiculous to take pride in the fact that some arbitrary tradition lasted for a few thousand years. So a bunch of people did this or that ritual for thousands of years...sucks for them! Why should I? (Never mind that the tradition may have evolved/morphed to the point that Talmud-era Jews would barely recognize it, let alone second temple Jews or earlier.)
Moreover, if I've already rejected the notion that the Torah is the word of God, why would I consider myself Jewish? How does being born to one woman versus another determine my identity and fate? If I don't believe, why am I "in the club" at all? Because the believers say that I don't get to choose my own identity? Shouldn't I be able to just laugh that off?
I went through a phase in which I refused to identify as Jewish, but it didn't stick. There is too much of my upbringing that I _do_ connect with, or remember positively, and feel good about. So I can't quite shake the identity. And lord knows I've tried.
Instead, as the sun sets on Tel Aviv for the last day of Passover, I'm writing a comment on HN and enjoying the challah I just took out of the oven. Let me check...yeah, it took more than 18 minutes to prepare. But what can I say? I'm Jewish, and what kind of Jew celebrates a holiday without challah? Not this one.
I think the point here is that identity, belonging, nostalgia, and a sense of connection to a larger community - not just a generation alive today, but a chain of generations - can be a powerful emotional driver for people. Simply put, the idea that "our ancestors" did this or that and the tradition and identity lives gives many otherwise rational people a feeling of belonging.
And while there's no shame in choosing to forge your own way, independent of the social environment into which you were born, it's no great honor either. It just is. Some people feel imprisoned by the narrative, some empowered, and some just don't care. And some - I suspect more than might meet the eye - are forever caught between a prison of arbitrary rules and the discomfort of floating listlessly through a strange and uncaring secular society.[0]
So if you managed to leave the baggage behind, all the power to you. For others, the baggage is inescapable. And for yet others, the baggage isn't baggage at all, but a source of positive emotion.
[0] I can't remember the exact page, but somewhere in Chapter 9 of Brachot the Talmud briefly addresses this conundrum. Search for "אוי לי מיצרי אוי לי מיוצרי". Hope I got that right...it's been many years.