Pointless Ratio on Braum's Ult?

It seems to me that some ratios exist on champions just to say you have them, and I can't figure out why.

One case in particular: 's Ultimate. It has a 60% AP ratio... and that's it. He has no other AP scaling abilities. What's the purpose of having a 60% AP Ratio on a 140/120/100 second cooldown?

's Boomerang Blade (Q) has a maximum 92.5% AP Ratio (on a single target.) This is pretty substantial, and has a 9 second cooldown. It's not going to justify going full AP, but if you gotta have a situational AP item, you're going to get a decent return on investment.

Now you could say there's a major difference between Sivir, a Marksman, and Braum, a Tank. You're right. But if you look at other champions played in a similar role, you'll see they have greater AP scalings that are pretty useful. has a total of 190% AP ratios on her entire kit (80% on just her ult!), and she is also a Tank/Support (AND her defensive steroid scales on resists, like Braum's).

: Between roughly 185% and 255% (depending on variable factors). He's a tank. The list goes on and on, from Sejuani to Shen, Amumu to Maokai, Nasus, Rammus, and Renekton too (even Renekton!).

TL;DR: What purpose does having such a low AP ratio on such a high cooldown serve? Is it just to say "his ult scales! See it has ratios!"