Because they don't know if they don't know the answer until they read it. Obviously.
Also, people may be very quickly scanning and clicking on a bunch of stuff. They are not carefully inspecting how many replies there are, and they might not even be noticing which forum it's in (for example if you view the latest posts on the forum, it mixes them all up, you see posts from various sub forums). So one example of why, is because they clicked on 20 threads, opening them in new tabs, and when they read yours they look closer, see it's about XP and think "Oh, well if this was about win7 maybe I could help but, idk about XP" so they close it.
Another big reason why people would read a thread and not answer is if the post was difficult to read, or rambling in it's content. Some people if they can't figure out what the heck is being talked about in a couple seconds then they close it. Sometimes I have completely read a post 2 or 3 times and still can't figure out what the person is asking.
Another reason is that by the topic wording, they think they know the answer, but then when they get into the thread they realize it's more complicated or different and they don't know it. So for example, with your thread title, one might read it and think "Duh, you plug it into the usb port and then share it" - because sometimes (really) users will post really obvious questions because there's something they just truly didn't understand (for example you might go into a thread with your thread's title and it's just a guy saying "Do I plug it into my computer or do i plug it into the router? Which plug is which?" etc.
I have created threads before where a ton of people read them and nobody answers, and yeah it is frustrating, but in my case I know it's because the thing I am asking about it kind of specialized and not simple. People are reading it in case it's not specialized and complicated so they could help me.
In conclusion, I think the reason for all the views with no answers comes from A. people who want to help but read further and realize they don't have an answer off the top of their head (although by the subject title they thought there was a chance they might have), [which raises a good point: If people made their decisions on whether to read and help based solely on the topic title, there would be a lot less replies around here I think] and B. the millions of people in the world randomly searching online for similar problems they are having, hoping to find a solution, and they just read the link title and visit the thread, they don't (and maybe can't) check to see how many replies there are.
Platypus and Animal have some good points I didn't think of too.
Since I posted in the XP forum I'm now up to 160 views with 1 reply (RolandJS, thank you), while this topic, posted 2 days later has already garnered 5 replies...
Why am I not surprised?
I'm not surprised, because your XP thread is about XP, and only a small % of this forum uses XP anymore. People can't just pop open their xp sharing settings in 2 seconds and look at how they are supposed to be, because they are not running XP. I assume (and I have no idea if this is actually true but I think it's a good assumption) that a lot of people don't even go on the XP sub-forum because it's not an area of interest for them. (Having said that, you *can* get XP support on BC, but it probably doesn't account for much of the support on the site just due to popularity.) [and to be clear, I am no spokesperson for BC, I am just a noob.] Also, a much smaller % of posters would know the answer to your XP thread's question. But most posters know the answer to this thread's question!
Also, if one reads your posts in this thread, they might get the sense that you're being really annoying, so, I'm drawn to wanting to view and reply to this thread. In the other thread you weren't being annoying so there would be no rush for people to pounce on you for saying something impatient and ridiculous.
Non-registered users can increase the view count. I have seen threads with like half a million views in a couple weeks.