It's partially just how stats work honestly.
Here on Tapas my first chapters generally have double or triple the number of reads compared to chapter 2. They always end up dropping down to 10-15 views before eventually dropping down to below 10. This isn't unique to just Tapas either (dA has 667 views on ch1, and 3 on ch95)(booksie ch1 has 1959, ch61 has 274, and ch 89 has 2 -so while the number of reads for the work says its 22k, it actually isn't "alive" in readership when the most recent chapter has just 2 views). What do all of the numbers tell me? I have maybe 1 to 3 readers across just those three websites.
My point is that the way stats have worked for me is that "chapter one will always have a statistically high number of views compared to any other chapters, independant of promotions and regardless of them". I don't really and haven't really promoted dA or Booksie and yet one of those has a large number of views, until you get to the more recent chapters. People aren't interested in a long-haul story. There's another stat that comes to mind - Ps4 trophies. Look at the FFX trophies: 1 for beating Penance, and 1 for dodging 200 lightning bolts in a row. More people have defeated Penance than those who have dodged lightning. There's no alternative or better way to do the lightning, but there's many ways and alternatives to defeat Penance - including making a pseudo-legendary weapon for Lulu.
Let's look at a story of mine that buys into Tapas's idea of making short chapters (but no consistent upload schedule). The result is identical to NTN (the above story's stats). Chapter one has more than four times the number of views than chapter two. Then interest tapers off and drops dramatically to just 1 view a chapter (with 1 like each), so I have just 1 person reading this story. I think the only reason NTN has a difference of four instead of six is because it's longer and I've been promoting it a bit more on here, so it takes a while before readership drops off (I also know from comparing stats years ago that my readership doesn't start to taper dramatically until ch10 of NTN).
Yes. I've compared stats across sites a lot, too much, and too often, and I really should stop doing it....