This is remarkable to me because I would say that right now is one of the most exciting times to invest ever. We are in one of the new platforms: VC hasn't been so interesting to me since ~2013, when cryptocurrency offered a whole new greenfield, or 2008, when the iPhone changed everything for mobile, or ~1998, when the WWW began to mature enough to allow greenfield everything. (With an honorable mention to VR - still the new platform of the future...) Just think about LLMs and programming! Programming hasn't been about to change this much, this fundamentally, since the invention of networks or timesharing, perhaps. How can you look at this and write it all off as 'shopkeeping' with no 'building a market from scratch' and 'just not that interesting'?
I think maybe the real reason is the next one: they're just older, and no longer have the gumption and energy to try to dive into the Shiny New Thing, and it's time to hang up their hat and call it a day, leaving it to the next generation.