Why might be a good question to start with. Why take two beloved 80's projects and try to squeeze more life out of them? 1984's Gremlins is fine just as it is. And Beetlejuice is great as a standalone film. Neither need retellings, continuations or rehashings. But such is the nature of the Mogwai.
You might be asking yourself, why are you talking about these two films in the same breath? Well it goes something like this. According to Blood Disgusting, Warner Bros. is remaking Amblin's 1984 Gremlins and they tapped Seth Grahame-Smith to produce the third film in this series.
The connection between the two films is that Seth Grahame-Smith is also writing the sequel to Beetlejuice for Tim Burton (the two previously collaborated on Burton's Dark Shadows).
So there you go folks. Cross another two properties off your list of films you wished were never retold or remade. Now if someone would just remake Purple People Eater...