Vulkan takes time to bootstrap. Even if I have a Vulkan bootstrap that works well for one project it may be unusable for another. If I have infinite time I'll use Vulkan but for a lot of people OpenGL is just going to be faster to iterate on.
Sometimes this development speed is important while at the same time using an engine like Unity or Unreal isn't going to provide the desired look and or feel. It's a rare intersection but it does exist.
Not necessarily. I see a few small games that roll their own OpenGL/DX11 engines due to unique requirements that game engines can't easily accommodate. I don't have any good examples off the top of my head but it's not uncommon to see indie game blog posts talking about why they're not using Unity/Unreal
The only downside I see to this is that the Vulkan space for AMD will leave OpenGL development in the dust. The OpenGL drivers for AMD cards have been sub par on Windows and Linux for a long time. This doesn't matter much for AAA games but smaller games and most non-game applications don't need and shouldn't want to use Vulkan.
That said as someone who does a bunch of Vulkan development on AMD platforms on Linux I'm really excited. There's nothing bad with some healthy competition.
I mean I love that DOOM and Quake are open source. I still play Quake with the VkQuake executable. It's certainly sad that games like that don't really get open sourced all that often but that's the nature of the business.
Games cost a lot of money to make. They're part of large international brands. There's a lot of stake holders and a lot of money on the line. I don't really blame publishers and developers for being cagey with that sort of IP.
I think that games that enter a more open space certainly have a longer lifespan. DOOM will be around probably as long as humanity just because the code is available and it's a fun game. But that long term thinking doesn't keep the lights in the studio on and doesn't help with the ever increasing complexity of game development.
I don't think we need to be so doom (heh) and gloom about the state of software as a whole.
Worth noting that this is a quote from the game Deus Ex and the 2% is relevant to the game's fictional universe set in 2052. It's meant to be more of a vision of a dark future at the given trend not necessarily a number to be used in the year 2000 when the game released.