Some people just don't find the distinction between "open source" and "source available" to be meaningful, or at least don't find it meaningful enough to warrant the outsized level of attention it gets. I can't speak for anyone else, but at least to me, "open" is pretty much synonymous with "available" in the way it's used in the term "open source", and despite this debate going on for years now I've yet to see an argument for why it makes sense for those terms to mean different things that doesn't essentially boil down to "because that's what OSI says". I don't find the argument that I should have to agree with the definitions from one specific organization for extremely generic-sounding terms to be particularly compelling, and if anything, the backlash anyone gets from conflating the terms purely based on those definitions as if they're the only morally correct ones just makes me even less inclined to buy into them. It's basically an attempt to trademark via astroturfing.