Why do some managers never say thank you?

Can we talk about how some managers just never acknowledge hard work? I had a boss who would only ever come to me with issues, but when I finally nailed a project, not a single word of thanks. It’s like they think we’re all robots who don’t need validation. I get that it’s a busy environment, but a simple ‘good job’ goes a long way. It really makes you question if they even notice the effort you put in. Anyone else feel this way? What do you do to cope with it?