During the coronavirus outbreak, Valve has obviously seen an uptake in traffic on Steam. Which has forced them to manage their bandwidth a bit. The company sent out a notice yesterday about some of the changes they were making to their services. Chief among them was the fact that they were now going to spread out updates to games out further than they normally do. Here's a snippet from the notice about those changes.
For games that haven't been played recently, Steam has already been scheduling updates for the next off-peak local time period. Beginning this week, we are now spreading these updates out over several more days. Only games played within the last 3 days will be updated immediately. As always, the game will begin updating immediately if you request to play it, and you can always initiate an update (or pause it indefinitely) through the Download Manager. We're also looking into additional solutions to help on our side.
So basically, if your game has an update and it's not what you would call an "urgent" update to play it, it will get pushed back. More than likely happening at the wee hours of the morning when fewer people are playing in order to accommodate it better. Which, if you're the average gamer, chances are you're leaving the client on throughout the day anyway, so auto-updates are no big deal. The coronavirus has hit a lot of streaming services hard. And while many internet companies have opened up their systems to take on more traffic and suspended caps and restrictions, it hasn't exactly helped out the services we use beyond giving them record numbers. Keep an eye on what Valve is doing because you may end up seeing more of this in the days and weeks to come across multiple services.