Because there are none.
If you opened a cafe, would you like patrons who come in, order
one drink and sit there the whole day staring at their laptop and
tapping your power supply?
Imagine your cafe only had 30 tables, and patrons like the above
took 15 tables. Geez WTF right? Where do you draw the line?
Do you like going to mcdonalds, and finding half the restaurant
occupied by kids doing their "homework" at busy lunch hour, and you
can't find a spot because of that?