In my experience, it's not just a lack of reading comprehension, but often some combination of an utter lack of curiosity, laziness and defeatism. Many other things, like video games, have escaped the realm of being reserved only for nerds and gone mainstream, yet computers remain something people just constantly assume are hopelessly complicated.

I know for a fact my mother-in-law can read just fine, as she spends most of her day reading novels and will gladly spend the rest of it telling me about them if I happen to be there. Yet when it comes to her cell phone, if there's any issue at all, she just shuts down. She would just rather not be able to access her online banking in the Citi bank app for weeks or months at a time, until one of us goes and updates it for her, rather than reading the banner that says "The version of this app is too old, please click here to update and continue using it." and clicking the damn button. If anyone points this out to her, though, she just gets worked up in a huff and tells us "I'm too old to understand these things, you can figure it out because you're still young." She will eventually figure these things out and do them for herself if nobody does it for her for a while, but her default for any problem with her phone is to throw her hands up and declare it a lost cause first. I've seen a lot of people have the same sort of reactions, both young and old. No "Hey, let's just see what it says," just straight to deciding it's impossible, so they don't even bother to check what's going on.