People who policy lurkers when there are actually things going on are most likely scum just trying to distance themselves from the main game and just trying to get a free lynch on town. Again, why would scum lurk if they know that they would be policied for it?
Same goes for town. The fact is that lurking is still a viable strategy, hence scum does it. Town often keeps itself busy in cross tunnels or whatever.
Meanwhile, people who call out... is not scummy.
Of course this is a spectrum, but yeah. I hope I made my point clear.
Well, actually, most of the D1 lynches nowadays are on lurkers. It's not a viable strategy as lurkers immediately get policied for it nowadays. From what I've seen from recent Mafia games, town rarely has a cross-tunnel D1, compared to about a year in advance ago when D1 was mostly some people backing up someone and some people backing up someone else.
As either alignment there can be times when you are not sure what you want to post - or if you want to post at all. This is normal. However, posting is generally seen as pro-Town while not posting simply lets the other players continue their trains of thought without interference (which is usually only useful for scum). Note that if if the game is at a standstill, lurking is profoundly harmful to the Town.
While some people are capable of lurking as a playstyle regardless of alignment, people don't like playing with lurkers in general and frequently criticize them for looking unreadable or scummy, making them choice policy lynches/vigs as well as objects of public ridicule. (Note that lurkers are not always unreadable or scummy, although the argument that they're not making the game any easier for Town is usually fair.)
Good analysis from MafiaScum.
Lurking -> Harmful to town -> Is scummy
There are town lurkers but they're hurting town, and leaving them alive is often bad IMO because you'll have very risky slots alive in the end game. Either these slots are scum or not scum but you can't reliably read them at a moment where you need to, or they're town needing to make a decision themselves while not keeping up with the game often.
In an ideal world all lurkers would be turboed. Unfortunately, in practice it's extremely difficult to differentiate between those who are scum and want to deny information from town, and those who don't know how to contribute or just aren't paying attention. Although you could justify policy lynching any slot that lurks, policy lynches in general are pretty iffy because you're essentially throwing the current game to improve the meta. Also people who decide to go after lurkers are often perceived as avoiding making meaningful reads (and sometimes they actually are).
ACTIVE lurking is scummy, some players are genuinely busy and have irl emergencies during a game, but if you are purposely lurking it is extremely scummy for one your trying to avoid attention, 2 bassicly what snaq said about it not contributing to wincon. 3 scum is lurking because town is feeling a lynch/scumpool and scum dont want to mess that beneficial lynch/scumpool so they lurk. though some new players genuinely dont know what to say which ive even felt when i started playing ps mafia, on fourm i think majority of lurking their is active lurking well because it is fourm and their is a lot of time to be active so its a little hard to non intentionally lurk