The annoying thing about reading, is how people switch off the filter in their brains when you are engaged in this activity, and feel free to behave toward people who are reading differently than they would people doing any other thing, and people who undertake the fundamental activity necessary for education and civilization are treated like freaks for having such a unintrusive, non-distracting, imposing-on-no-one-else pasttime.

You've been there in at least one of the following scenarios, haven't you?
And you just can't give the italicized responses, either, because that's rude.

A: A book is a conversation-starting device!
What'cha reading?
If you had ever tried reading yourself, you would know that it is a mental activity, which is disrupted by your pointless attempt to talk for the sake of making noise, however minimal the degree of said mental activity a conversation with you actually entails.

B: No one would possibly consistently engage in a practice he finds satisfying, unless it is the onset of a professional interest!
You read so much, when are you going to write a book?
When are you going to open up a brewery?

C: One of the following articulated behaviors is rude. The other is apparently perfectly normal:

Since you are staring slack-faced at that screen, or lying limp in the sun, you are clearly not doing anything, so I am just going to start talking to you.

Since you are actively holding up a book in front of you, and turning its pages, you are clearly not doing anything, so I am just going to start talking to you.

D: Did I mention double standards?
Hey, don't take out a book during this meal, this performance or while other people are in the room! That's so rude! Now excuse me while I turn my attention to a phone screen for the next 20 minutes, with slow-reaction grunts to indicate that I am not really listening.

E: Warning: side effects of reading may include literacy...
Would you mind undertaking additional duties for no additional compensation, or on your own time, simply because you are the only person available with a basic comprehension of English grammar and spelling?