Why does your laptop take so long to update?

Answer 1

The nature of laptops is that you usually shut them down when you want to move them, so you're more likely to notice a long update process because you have to sit there and wait for it. If you update a desktop computer, you can usually walk away from it and just let it take however long it takes to shut down.

So part of it is an observational artifact: it's not that it takes longer, it's that you notice it more.

Another part is that laptops are more likely to be on a wireless network, and those tend to be slower than hard-wired networks. This is coupled with the fact that laptops often have lower-power (slower) processors, so it's perfectly normal for a laptop to take longer to perform any given task.

Finally, laptops are often turned off when not in use (a lot of people leave desktops running all the time), and are usually set to update when not in use as well. This can allow a big backlog of updates to build up before you finally choose to perform the update. My wife's old laptop recently got repurposed and brought back into service; there were something like 70 updates pending since the last time it had been updated.