I work a desk job and I used to be too lazy to get up and get a drink, and I tend to also not notice when really focused on something. When I'm outside, I notice the thirst a lot more, but in a climate controlled room sitting at a desk, it's less urgent.

So I keep a bottle next to me all day and refill when I empty it every couple hours. I don't count how much I drink, and I don't think the "8 glasses every day" thing is particularly relevant, but I am plenty hydrated throughout the day (probably something like 6 cups of whatever without thinking about it, maybe more).