The sense of smell is ancient and has served animals well since forever. That's why the close coupling. The olfactory bulb is like a part of the brain in the nasal cavity.
Your eyes are actually an outgrowth of your brain and they're exposed right out in front. The eyes have their own extra defenses though.
Still, we have highly-effective sensors in other parts of our bodies, further away from the brain, and surely we could drop that check somewhere else. At least when it comes to eyes, one can make the argument that they should enable split-second reactions to run from that predator as soon as you spot it, so they should be as close as possible to the mainframe... whereas nobody is going to die if they can only smell wolf poo a second later.
>whereas nobody is going to die if they can only smell wolf poo a second later.
I'm still alive today because I can detect smoke very early. This ability has saved me from indoor electrical fires and wildfires. Hunter gatherers who lived in makeshift shelters probably depended even more frequently on this ability.
Signals can travel relatively fast across the entire length of a human central nervous system. Proximity to the brain likely benefits signal-to-noise ratio more than speed.
Your eyes are actually an outgrowth of your brain and they're exposed right out in front. The eyes have their own extra defenses though.