I think part of it is Lobsters has an "average karma per comment / post" feature which means Lobsters users usually don't post a lot of "wow!" or "thank you!" comments and instead prefer to speak up when they feel something substantive is meriting attention. I've posted threads there that were #1 for a day and got like two comments. I've seen other smaller threads I've posted explode with comments when, for instance, there was a weakness in my project's design. It makes Lobsters a hard crowd to please, although the important thing to understand is they actually still love you. The website design just has different incentives for discussion.