Sometimes it shows enough information but most of the time, it serves no purpose.
Go to ARAM, spawn, take no damage from minions or otherwise. Get 100-0'd in less than 2 seconds by enemy team. Death recap shows 2% from one source, 20% from another, 3% from another and then 5% from somewhere else. 2+3+5+20=100?
Whoever put it together either can't into basic math or the entire screen is useless.
If it wasn't for the death recap I wouldn't know how much damage the enemy Flash did to me.
Yea, there are times I feel like I got bursted 99-0 in 0.02 seconds and I go to see just how fast the guy bursted me (mostly just to see if it was even remotely possible to react or if I'm dying because my teammates fed) and then it says damage over 3.5 seconds and obviously some minion damage I took long before the burst even started is being included in the death recap.
Would love to see a sequential time listed sources of damages alongside remaining hp at each point.
Your title is kinda misleading...
Death recap has no point in its current state, but it could be made useful
The sad thing is, if Riot took the time to implement things like replays and a better death recap, some people would automatically improve at the game
From what I've heard and seen over time, the death recap was coded weird. I'd look at it myself if I had a legal way of doing so :c
The death recap is there so you know what is killing you. With that knowledge you can build against it. The weird percents is often due to how so many enemies can aid in a kill but only three are shown. You can fill in the rest of the percentages with the other enemy champions. The number get even wonkier when you have someone basically ks, since it with kick out the third main damage source for the guy who got the last hit.
To show you how much damage the enemy 
did to you.
LOL! I would like it if it was accurate for sure.
i'll just leave this here
The death recap had to be worked on along with the new rift. It's not a good use of resources to fix the death recap when the game has other problems.
The most consistent death recap was from Guardians of Middle Earth where it shows every single instance of damage in a list. So if you died to 5 auto attacks, it will show the damage from each one.
