Ignite Burning Arrow - Why not?!

So I was following this (Ignite) Elemental Hit Guide which stated league starter etc etc. Not realising I needed the jewels and ended up taking Avatar of Fire and wondering why only 1 every 3-5 hits were doing damage. Long story short, I switched to Burning Arrow until I could acquire these jewels.

As luck would have it, the Burning Arrow Jewel dropped for me, allowing for an additional stack of Ignite.

At this time Fireball was doing way more DPS for me and to be honest clearing trash faster (I kept messing around with options) But bosses, with the extra ignite are melting much much faster.

I'm curious as to why Burning Arrow - if it can potentially have 3 stacks of Ignite compared to Ele Hit/Fireball/Arm Brand can have max 2 - isn't used in Ignite builds?? It would mean the Initial hits from Elemental hit/Fireball etc would have to be 50% stronger, right? Does the damage scale that badly end-game for burning arrow? Or is it to do with Up-time i.e harder to keep 3 stacks?
I can't find any threads about this!

TIA

Tempest burning arrow ignite elementalist are pretty good, damage is ok and ignite prolif from ascendancy offers great clear speed, i can recommend this build personally, played it in incursion and it was amazing. Core items are tempest/stormfire/dyadian dawn. Mathil have a guide for this build on his channel.
https://www.youtube.com/watch?v=Rrzips4OcC0
Some example of how good this build