Why are SMNs not getting new Egi?

[Kabooa]

It's much easier to balance three Egis and a DemiPrimal than 6 Egis and/or 6 DemiPrimals.

While true, there's no reason you can't feature the Egi's as part of spell animations. This wouldn't be a matter of balance but would cement the Summoner visually summoning a creature to execute the attack rather than themselves.

For example, if Painflare animated as Demi-Ifrit blasting an area with flame.