I believe it's a bunch of different variables, but servers being the top reason. When i bought s2, CTRA was in full swing. Bump and Jump was a cool down period for us hardcore GTR / STD / TBO frequenters and we had several drift servers rotating tracks, each with either all learners or really good tandem drifters.
Ever since CTRA dissolved, i want to say lfs took a great decline with updates doing the same around the same time creating no aid what so ever. Bring back servers like noobs sumo, banger racing, and soccer and lfs will see a good incline as these servers offer a experience that you can't duplicate.
Have a dedicated night of racing for each class and keep the server open that way when people see it halfway full, they'll join and before you know it, it'll stay full like cg throughout the week.