Many rooms aren’t meaningfully used in a day, a week, or even longer. That’s OK as long as they don’t have a real impact on other users - and for the most part, I don’t see how that can be the case, since most are far off and usually it’s forms of active use that cause lag.
Many places you take others to for play, like the clothes shop in Woodford, the veterinarian on the Isle of Wing, or Takefumi’s ramen shop. They’re not intended as social hangouts; regular occupants would defeat their purpose unless they’re instance rooms. If there’s an issue, it’s that people often don’t know they exist, which is what the various IC (descriptions, maps, newspapers) and OOC (area info, forums) methods of informing them are for.
Some of those single characters have a specific roleplaying purpose, i.e. they are there to staff a shop, tend bar or work the stables, and at times other than ~7AM UTC they may have company. They might also be enjoying themselves exploring, tweaking an area or a script - since you can’t edit from elsewhere - or just idling somewhere to contact if people want.
Wolfery lacks a few things that provide environment aside from rooms and exits, e.g. looktraps/details, [fake] objects, containers, inventory, a library of scripts and uses of them. Some of these are coming, or can be worked around with profiles, but extra rooms help.