One additional factor that I think influences people who read The Sequences and then LessWrong on a regular basis is that the pace of receiving highly useful ideas while reading The Sequences can be very high while the pace of receiving highly useful ideas from lurking on LessWrong is much slower. It's a move from several new useful ideas per day to one new useful idea per week or per month.

I don't think this means the weekly to monthly content on LessWrong is low in value, it just occurs at a slow pace (which is to be expected). I'll also mention that I've asked long-time members about this before and they said the pace was actually always slow with one great thread occurring once a month or so.