Help me understand Unending Hunger Cobalt Jewel

Sorry if this is a dumb question but they are my forte and my raison d'etre ;-)

Started playing this game mid last season and this season I'm playing summoner and loving it.

I keep seeing Unending Hunger being recommended as a must have and it is on my acquire list when I have funds. It was ~3EX but seems to be dropping.

My question is why is this jewel so good and recommended?

I've done some research and I've seen some people say they use it to increase AOE. I've seen other stuff saying the Soul Eater buff helps with map clear speed.

I may have done it wrong but I tried adding this jewel into my build in Path of Building but could not see any change in damage number.

What exactly is it that makes this good and so expensive this league (I've seen old posts saying this was really cheap in previously leagues and where I guess Necromanacer wasn't as popular).

I'm not experienced summoner nor I have played summoner build in Harvest so this is my mile-high interpretation.
Unending Hunger gives your specters 50% chance to gain Soul Eater buff for 20 seconds. This buff increases attack and cast speed, also character size, on kill. This means your specters will be gradually getting buffed as you progress through a map. Specters are extremely powerful this league, especially certain ranged types that dominate the meta. You only have few specters so this jewel will let them to get Soul Eater buff and stack it to increase their already high damage output.

Your spectres have a 50% chance to gain soul eater each time they get a kill - for 20 seconds. After gaining the soul eater buff the spectres will get 5% attack and cast speed for the remainder of the 20 seconds every time they gain a soul (one of your spectres will gain a soul each time an enemy dies within a fairly generous radius of them) these souls are the same souls you use for vaal skills so only 1 spectre gets a soul per enemy killed and it'll greatly dampen your ability to use vaal skills fyi. But its not uncommon to have spectres basically double their attack and cast speed in open maps using this gem.

That said, as a long time summoner no way would I drop 3ex on it. Its good but not THAT good - and it does little to nothing in some of the really hard single target fights.

Thanks for the responses and information that does help.

Yeah, I'm currently put off by the ~3ex price of the jewel as it's beyond my budget.

Looking back at last season, the jewel never got over 100C in Delirium league: https://poe-antiquary.xyz/Delirium/Jewel/Unending%20Hunger/1745

I was wondering the same. Seems like two other items have the Soul Eater buff. One being the belt, Soulthirst. It has the buff any time you use a flask. I wondering if it could be a cheap way to have Soul Eater.