One thing about "last read" is that it doesn't track the "newest read release" chapter. If you're the kind that likes re-reading old chapters, you might get lost.
E.g. you read until chapter 150. Then you decide to start a slow marathon on reading old chapters. After a month, you reached chapter 50, and decided to get back to where you were before the marathon. Behold, the scanlator managed to release until chapter 160 since last month. Now you don't remember the latest chapter read, nor you remember when that you started the reread marathon. How do you determine that the newest read was chapter 150?