@Tcof
Theoretically, why not.
However, defining the behaviour of such a button is not that obvious.
For example, if the first chapter is available in several languages, then the button would have to choose one arbitrarily (especially if the default language for the user isn't among them)
It might also happen that for whatever reason, chapter 1 is missing in the reader's default language (for example a release that was deleted by its scanlators). So the button would have to choose between chapter 2 in the default language and chapter 1 in another language.
But even if there is only one available language for the releases, it is possible that two different group have uploaded this chapter (the latter probably with the pretext of better quality), and the button will still have to choose arbitrarily which one it gives you to read.
Things get even worse when there's a pre-serialization oneshot before chapter 1. Because the button would have to arbitrarily choose between chapter 1 and the oneshot.
So, it is likely that such a button would be a hassle to develop, and would not satisfy every reader with its behavior.
Of course, this could be solved by giving the user the possibility to configure the "read 1st chapter button", which would add to the development complexity, and force the user to play with the settings probably for a longer time than would be required to directly find the desired first chapter in the release list...