Sometimes she thought the reason they got along so well was because she really understood him, better than Lily, far better than Ted or Marshall. Marshall had been quite happy to fall in love and settle down with the first woman he'd ever dated, and, although Robin loves them both, admires their picture-perfect relationship, she can't help the thought that he'd been quite happy to settle for her as well. Lily, for all her insights and abilities to read people, had willingly settled no less, and Robin can't help but feel that anyone whose philosophy was so completely antithetical to the freedom that she and Barney craved could never truly understand. As for Ted - Ted was so ready for commitment, so desperate to catch up to Lily and Marshall so they could all begin their 2.5 kids-and-a-dog, white-picket-fence-suburban bliss - complete with backyard and minivan - that he couldn't conceive of the fear that gripped him and her every time a relationship seemed in danger of becoming too serious.
It was highly ironic and quite sad that double dating, wine-and-cheese tastings, weekends away at bed-and-breakfasts in Vermont, Sunday brunch - all those couple-y activities that were quite wasted on her and Barney - Ted would have embraced with unabashed enthusiasm, if only he'd had someone to share them with him. They'd tried that once, she and Barney; they'd tried to conform to the others' ideas of what coupledom meant, of what it should be - and the results had been catastrophic. She'd lost herself to the fetters of commitment; and, while breaking up with Barney had been heartbreaking (because she really did love him - loved spending time with him, loved the sex, the raunchy jokes - he was the perfect package) breaking out of the girlfriend mould had been like being set free. She just didn't seem to work that way (and maybe that's what the world had been trying to tell her with the Don fiasco - maybe she just wasn't meant to have a committed relationship like everyone else).
She knows its the same way with him as its been with her for years now; meeting someone new is thrilling, the flirtation, the attention, the foreplay - it's all so much fun. Until the moment inevitably comes, about three weeks and maybe four or five dates in, when he tries to define the relationship; when he tells her that she's clearly a family-oriented person, and he sees real potential between them for something more than casual dating; when questions like "so, where do you see this going?" and "does this mean I can call you my girlfriend?" start coming thick and fast, and all of a sudden the cage is back, and she can't think, can't breathe. Because asking for a commitment - any kind of commitment, no matter how light - after just a few weeks is clearly too much, too fast. Because the need to protect her heart is beyond paramount.
She knows that he understands this; that's why he's long given up any pretense at monogamy, even the no-more-than-three-weeks-with-the-same-guy, hardly-qualifies-for-the-label variety that she espouses. She gets him, understands why he functions the way he does, and frankly doesn't really see anything so wrong with his basic premise - keep your heart apart, and live through your other senses; see, hear, taste, smell and savor love; feeling it is overrated anyway. So that's why they're here, she thinks, tentatively trying once again to act on this thing that's still between them, that never really faded - only this time, they're doing it their way. They're not going to define the relationship according to Lily's rules. They're not going to do the couple-y stuff with Lily and Marshall anymore, because they're just boring, lame, un-awesome, everything that Barney and Robin are not.
And they're not going to put limits on each other, force each other into some kind of straitjacket of fidelity. That spelled their relationship's doom last time, and there was no reason to think it wouldn't at this stage. They were just hanging, the way they both liked it best - drinking scotch and smoking cigars, playing laser-tag, going to strip clubs - and spending their nights together, wrapped in each other's arms. That's why she was sitting here tonight, in their booth at McLaren's, calmly sipping a beer while watching Barney hit on some leggy blonde by the bar. This was them, this was the way they operated - and she wouldn't change it if she could. This way, he'd come back to her at the end of the night, because she was something light, sexy and fun. He'd come back to her, because this way, she was no risk.