Here’s the thing, Jensen is a private guy. Just look at the way he is about Danneel. There’s no denying the way he lights up when he talks about her or when a fan compliments her, but they themselves are pretty reserved in public which has led to (stupid) speculations about their marriage. Remember when he was telling an interviewer about how he proposed? He kept the actual proposal private because he keeps his relationship with the people he loves most close to the chest.
When J2 were younger, they were all about the PDA at events and interviews and such. But now they know about fanfiction. They know about wincest (hell, it’s been mentioned on the show multiple times), and J2, and tinhatters. Jensen even said his mother used to troll fansites defending his honor, so to speak. They’ve seen as much of the dark side of this fandom as they have the good (they’re just too classy to mention it) & it’s no wonder they’re wary— especially now that they are both happily married, much to the chagrin of some of the fandom— of displaying overt affection when they know it’s going to be analyzed and giffed and put on youtube. As early as ChiCon ‘07 Jensen knew what connotations we added to their friendship when he said ‘that’s gonna end up on youtube’ after Jared hugged him. Remember the eyelash story? They were conscious of what fans made of their public affection even when they didn’t censor themselves in public as much. It only makes sense that as they grew more mature and started their own families, they’d want to tone it down in the public eye.
From their body language at cons, you can tell they still love each other. They’ve stated numerous times that they’re like brothers, they’re friends for life, etc. They’ve known each other for years now. When you spend that much time with someone, when you know him that well, you reach a level of comfort that doesn’t require constant affirmation. They’ve only ever had one fight and right after, Jensen went to Jared’s trailer and hugged him. Jensen himself stated he could tell you a story about how Jared is in any situation. When he’s upset, Jensen can probably tell with just one look at him. How many guest stars have commented on their chemistry? S.E. Hinton said they are clearly best friends, even if they don’t feel the need to be with each other 24/7 (because they practically already are). Felicia Day said it was like a romance novel on set. Still don’t believe me? Just look at the most recent gag reel. They light up around each other, they make each other laugh like kids and they showed plenty of physical affection while doing it.