That is surprising and yet it isn't because if someone is lazy they might check it out of curiosity and still decide they're too lazy to respond. Its kind of like that Role-playing Game etiquette topic about how people see the game.
I think sometimes a gridlock kind of happens where someone doesn't want to react until someone else reacts, but that person is waiting as well. It ends up that nothing happens for a while. It is very difficult to get things done. I am currently Dungeon Mastering 3 games and participating in 2 more (Both on this site and various others), and I have several characters that I know I can count on to post consistently and several that I know are going to be the last to post. I tend to just give the players that post more some small rewards (They get to describe more of what they are doing and get more bonuses and such) while the players who post less I just use the bare minimum details to complete the action in the most straight forward manner (I can't ask for qualifications, because they take forever to respond). It is all in all a very frustrating way to game.
I would say I'd have to be a bit careful with my words here, so as to avoid being a hypocrite, yet perhaps it is because of how I have be on both sides of the situation then I can offer my own insight on the subject.
Any roleplaying game, whether play by post, Skype, Roll20, or together at a table, is generally a cooperative effort. There might be times where one character may find themselves in the spotlight, yet give and take it should be that all are participate and given attention.
Laziness can be a problem, though this could simply be focus. In person, most have a few hours set aside to roleplay yet online it may simply be whenever one is available or can get in a post. Even then, detail and effort is still very important.
Again, if there's been any concern with my activity it is something I'm trying to work on. Everything should be good to go a lot smoother once I have a change of schedule next week, particular with three days off. Right now though it's just been a little bit of a struggle, especially since there's been so little availability to post during work.
Edited: Thomaslee on 25th Jan, 2017 - 2:11am
Thomas this post wasn't about you so don't worry about it. There are slackers in our party that haven't showed up in a long time and they don't even say anything. They might disappear forever only to come back months later asking where their character has been.
I will be honest, I have been one of those people that check the games I'm involved in frequently but I do not always post every time I check. Some of this is the way my creativity works, it comes and goes at times and I suffer from writer's block on occasion. I am not a fan of short one or two sentence posts and I try to avoid them so if I don't feel like I can contribute anything decent I refrain from posting and usually I am able to come up with something within a day or so but if it takes too much longer than that I will go ahead and post something short and less detailed just to keep things going.
As a Game Master I try to mitigate this behavior from the players by making my posting policy clear, which includes being sure that players understand that lack of participation could result in the death of their characters (And I'm usually not very nice when their characters die from lack of participation). I will give some leeway the first time a player "Flakes out" and try to contact them to get them involved again and I will give them at least one warning in the associated support thread to let them know that their lack of participation may be the death of their character, but I tend to not do this a second time.
I currently run two games and one of them is bogged down; unfortunately I think that this is largely on me as the Game Master because I've been really struggling with it and having difficulty focusing on it. I think that, in general, the Game Master is the primary player that moves the game forward so if the Game Master is struggling to focus on the game the players are going to have a hard time as well.