Questions from Season 2 (spoilers)

I just started watching the series a month or so ago, and have made it through the end of season 5. The only thing I can't really figure out is why they showed us Shane and Andrea hooking up in the car and then never took it any further. I wasn't sure if it was to show us that no, Shane really *wasn't* better for Lori since he couldn't stay faithful to her - looking at it from another perspective, Rick would have said no under similar circumstances. Was it more it to show that Shane was wiling to take advantage of someone physically and emotionally weaker than himself? I mean, Andrea instigated the encounter, and she was certainly no innocent babe in the woods, but an argument could be made that she was still emotionally compromised from the death of her sister (a button Shane had just kicked hard) and she was also coming down from the adrenaline rush of almost being killed. An argument could also be made that Andrea still might have seen Shane as a defacto leader of their group, and he was further in a position of authority over her because he was teaching her a skill she felt that she needed to know in order to survive. Was it a backdoor way to introduce sympathy for Shane, kinda giving us a Devil's Advocate for this character that everyone else seems to be distancing themselves from?

Yes, I'm probably overthinking this. I will admit that Shane is my favorite character, and to that end, I would have preferred the writers using the Shane/Andrea angle to separate the two from the rest of the group in order to explore these two characters further so we could keep Shane around a little longer. I just couldn't ever figure out why they devoted time in the series to their kinda sleazy encounter and then never really addressed it again.