Because Gai always makes things more awesome. And you all know it! As for Samurai, well for spoilers Kakashi has come home to see the visitor and he is rather not impressed with this idea. And no, still haven't gotten to the blog yet.
Gai thought it was hilarious when Kakashi finally decided he was going to properly court the pink haired girl. Gai himself had been happily married to a beautiful civilian woman since the tender age of twenty-two. She was like a mother to Lee and they both agreed that the boy was quite enough in the way of children, and she worried enough about Gai when he went on missions that she didn't need more little ninja to worry over. So it was from his happily, privately, very married life that Gai had his giggles over his friend.
Of course it wasn't sporting to think that Kakashi was a total dork, but what other choice did Gai have left to him? Kakashi had never dated, never had any open crushes that he harbored, and read erotic books in public as though everyone did—the man didn't know up from down, romantically, save for the day he had been out walking with Gai and seen the pink haired girl for what seemed to be the first time.
Gai of course knew that the girl had been Kakashi's student back in the day, but that had been what? Ten years ago? Numbers like those being thrown around weren't very youthful, but it did serve a point to illustrate how oblivious Kakashi really was. To not have noticed the delicate little flower becoming the poisonous beauty she was now, well that was something Gai almost expected out of his friend at this point.
Because the girl was something of a poisonous type—perhaps still a flower, but not a delicate one. And that was exactly why Gai thought it so hilarious when Kakashi set his sights on her. Not only did the man have little to no idea of how to properly court a regular woman, he had chosen one of the scarier ones in the village as his prize. It was only sporting, then, that Gai decided to give his rival a few tips and pointers—with heavy disclaimers that he hadn't tried them out in a decade and a half, so to be wary playing with dull weapons.
Kakashi's string of "training-related" injuries only indicated that he hadn't heeded the subtle warning in Gai's playful advice. A sweet tempered woman wouldn't require weapons to be used in courting her, rather a woman with a fierce attitude would suit that bill. But eventually Kakashi did start to catch on, on his own as usual. Gai didn't take any offense, however, his genius friend had always found his own way to excel and this was no different.
Soon the pink haired girl was sweetened to the very dorky side of her former teacher—they apparently had the same hobbies of apartment-gardening and weapon-shopping, and got on famously with their cooking skills. Her smile in the marketplace when they went grocery-shopping for a dinner in was one that every kunoichi around recognized as a smile of triumph or satisfaction, while Kakashi—tugged along next to her by way of their clasped hands—merely had a blush staining his face. He was happy to be there, his expression said, regardless of how Sakura's own attitude nearly crowed at her catch.
She had realized that despite how awkward Kakashi's romantic skills were, they were honed in an effort to catch her. It was in the interim, where she figured out his intentions and her reactions, that she decided he was worthy of her affections. Gai and his wife could only grin fiercely whenever they saw the two, glad that their longtime acquaintaince had finally decided to settle down.
Because that was what would happen—regardless of whether or not either of the two in question knew it. Kakashi was far too traumatized, deep down somewhere, by the experience of courting just this one woman to ever try again. Besides, he was happy with her because she had caught his eye for a reason, whatever that reason was. And the girl was now far too taken with this man that had reached out for her and her only, and deep down somewhere she was too flattered by that attention to ever direct her affections elsewhere.
Gai was happy for his friend, although he still chuckled at the man to his face.