I think the reason people often ship two straight male characters together (beyond queerbaiting, and fetishization) is because male characters are typically written better. The female love interest is just that, a blank object who's only purpose is to be romanced by the protagonist. If you're lucky she may be a #girlboss and use a weapon or be 'smart', but we're never shown what shes like, what would make us or the character love her.

The best friend on the other hand? We know what he likes, whether his warmth and naivety balances out the hard cynicism of the protagonist, we will see how their friendship formed and how they relied on each other. What forms their bond.

So naturally that bond seems more real, theres more chemistry between friends, who do love each other (because platonic love is a beautiful thing), than between to characters who must kiss because the story says so. It's a pity, because I think showing that platonic love is important, especially when you think about how society already shames men for expressing their emotions in any capacity beyond pretty much anger and horny.

It also doesnt help that people are still starved of good queer rep in many forms of media, with queer relationships and characters remaining in the background or being reduced to stereotypes. While it has vastly improved since the peak of tumblr circa 2012, theres still much to be done. *cough* WLW relationships *cough* nonbinary and trans characters even being seen *cough* literally anything beyond two cis white guys *cough* but yeah, thats just my thoughts.