While DC is getting their movie universe together, their TV show universe is already in full effect. Arrow, Flash, and Gotham became instant hits, and Legends of Tomorrow looks like it will be another. So why can’t we have the TV universe crossover with the movie universe. Let’s see Miller race Gustin.
DC Entertainment Boss, Diane Nelson, told Variety the reason why they are keeping the universes separate.
We’re so talent driven. Focusing on keeping everything in a single continuity “could end up handcuffing our creators into trying to work with the same storyline or force them to hold back characters or introduce certain characters. Ultimately it hinders the ability for someone like (showrunner) Bruno Heller to come in and create Gotham.
Source: Comicbook