Why is Hypothermia gem good?

I've seen several build guides that recommend Hypothermia gem, and I'm playing Winter Orb and I've seen several that say it should be used.

But I get way more damage from Awakened Added Cold damage or even Ice Bite because I have 12 frenzy charges.

Can someone explain why Hypothermia gem is better?

If you get more damage from a different gem, then chances are it's better for you. However, flat damage may not scale as well with higher levels of gear invested. I certainly wouldn't calculate having Awakened gems unless you have matching quality of gear. After all, a single support gem will cost you 3 ex in Scourge or 5-6 ex in Standard. Leveling Awakened gems is also a hefty investment (can level a regular version to 20 5-6 times for the exp required to level an Awakened version to 5.

Are you looking at the game tooltip to compare or using PoB with the proper options set? The more damage mod on Hypo isn't reflected in the game tooltip, since it's conditional on enemies being chilled.

No I'm just looking at the 30% more damage mod on hypothermia, and how that isn't really very close to the damage from some other gems. Unless I'm missing something, it seems to me there's several higher damage gems.

That's why I'm asking, because clearly many other people disagree and use it in their builds. I wonder why....

One example of why is that added damage effectiveness isn't great on Winter Orb. 29% more damage on lvl 20 Hypo is going to outpace the flat damage from Ice Bite on many builds. Throwing a bunch of added cold at Orb can offer diminishing returns pretty fast. Awakened added can be better because of the +1 increasing the base damage of the skill, but that might not always be the case for all builds. That also gets expensive and is more of a min/max thing, so a variety of builds won't include it based on that alone.

Simply looking at the gems isn't going to tell you much behind the reasoning. There can be all kinds of reasons to choose one over the other, but it can vary quite a bit based on the build and the goals of the build. PoB will give you a much better feel for which gem is the best fit for where you're at with yours.