Why do people often say users come "from" places? How does one come from a particular website? Is it not commonplace to use a variety of different websites at once for different and/or sometimes even the same purposes just to be able to communicate with different individuals?

For example, if you come here and only here, why? Why do you limit yourself to 4chan? If you only go to other places and just take visits here, why do you just visit or choose whatever this website is as your primary place of visit.

I don't understand it. Its so easy to consume vast stores of information on the internet; going to only one website would be boring since you'd go through all interesting information there and still wind up with free time.