Because, think about it. Let's assume techno-feudalism is complete. Every piece of infrastructure is going to have usage fees attached anyway. Everyone is using AI, so are you going to be the only one not using it? Of course you'll use it. It's a structure where everyone has to rely on a specific corporation's products to get anything done, meaning the wealth will automatically be absorbed back to them anyway. So why would they go out of their way to commit a massacre?

From a cost-benefit perspective, I think it's a terrible idea. In the case of a massacre, long-term instability makes it hard to build a supportive faction. But if you provide just the bare minimum to survive through UBI, the capitalists will gain a loyal faction that will act as their Red Guards to attack dissidents, which I think is much cheaper in the long run. There are already plenty of people who blindly defend corporations even when they do terrible things, right? In my opinion, UBI is simply the cheaper option. Historically speaking, post-massacre recovery has always ended up costing much more.