When I was looking at the stats for they don't seem to be any greater than what I would expect for an armor set at that level.

And I can see that someone might want them for the cosmetics. So there is that.

Is there something about these armor sets I'm not seeing that makes them worth the additional crafting materials cost?

That and other similar schematics stem from an older content cycle of SWTOR (I think 4.x in this case). At the time they were the best you were able to learn from the crafting trainer or by re-engineering and so to speak the best gear available for players not doing operations or PVP, thus requiring the at the time end game materials too.

When the next expansion of the game was released, new schematics coming with then had better stats and needed the next rank of materials introduced too, making the old schematics sort of obsolete, at least for stat values.

Bioware usually doesn't change the materials later, they only make sure former special materials like isotope stabilisers and the like are made available from the Jawa scarp vendors when new versions of them come with a new expansion.

The look of the armour though still is somewhat unique and still reason for some players to get it crafted or buy it from the GTN.