It used to be normal for steam sales to be somewhat rare and surprising, but the tradeoff was that it was the norm for big and popular games to have staggering discounts.
In 2012, Terraria went on sale for 25 cents. Valve sold the entire Half Life family for like two dollars. AAA and big name games would go for 80% off or more, back when that actually got you a full game without microtransactions or significant DLC to buy.
People got excited about the sales because you might wake up to find the game you really wanted for $60 was now a few dollars.
Objectively "Incredible" deals are a lot less common, and old stuff doesn't have massive discounts anymore, sticking with "just" very good discounts.