Why would I opt for a network topology that restricts what devices/operating systems I can safely use on my network? Especially when I already have a solution t

Why would I opt for a network topology that restricts what devices/operating systems I can safely use on my network? Especially when I already have a solution that doesn't restrict me in this way? It's like saying, if a person walking around at night gets mugged, it's a "them" problem for not carrying a weapon to defend themselves. Uh, no, let's create an environment where even a completely unprotected child is safe. Oh wait, we already have.