Riot: Why do resurrection passive cooldowns not scale?

Towards the late game abilities have lower cooldowns because teamfights become more frequent and objectives become the main focus of the game. There are several abilities that don't get reduced cooldowns later in the game, though, despite being ridiculously long. Zac is the prime example. His passive cooldown is a whopping 5 minutes, meaning you won't have it in a majority of fights come late game. I suppose it's a matter of opinion but I happen to think Zac's passive is one of the worst of these passives. It takes 8 seconds for the blobs to come together and with the new AoE Smite in Season 5 killing the blobs is easier than ever. I estimate I see Zac's passive actually cause him to live once out of every four or five times it procs. Taking into account all of these factors I see no reason why this ability remains having a 5 minute cooldown in the late game and why other very long Static Cooldown passives don't get lower throughout the game.