Why do stock prices consistently increase for extremely stable and predictable markets?

I'm invested in many boring companies like:

1. Waste Management
2. Walmart
3. Proctor and Gamble (via VDC)
4. American Water Company (AWK)

and there are similar companies I have in mind, like Kimberly Clark, MMM, and KO.

Many of these picks have performed phenomenally recently, e.g., WM, which often outperforms the S&P 500. It makes sense that these are great picks because of their moats and wide market share.

But at the same time, shouldn't the growth of stable companies like this be priced in? If profits/revenue are extremely predictable in the future, why would the stock price regularly grow? Shouldn't the market just buy in until it believes WM is fair valued and then the stock price should behave roughly flat?

I realize this is company specific, but what makes WM such a great long term performed and not something that is just priced in? Yes, trash isn't going anywhere, but doesn't the market know that? Same with water, or consumption of soda?