Stone, Lime, Adobe/Cob Construction: Avoiding Cement?

This is my first post. I am building a house in a high, wooded region in Central Argentina. The climate is arid in winter and humid in summer. I have already built a stem wall with stone collected on site, laid in a lime/sand mortar with some volcanic dust added. No cement so far. Yet here in Argentina, even those that build in cob (or with unfired clay bricks and a cob mortar) tend always to lay a sand/cement course between the stem wall and the first laying of cob. They call it 'la capa'. Despite having read that impermeable cement membranes are generally not recommended in lime/earth construction, most here seem to do it anyway, as a kind of 'just in case' measure, not only to top off the stem wall but also in the floor, by always adding cement to the sub-floor mix instead of making up a pure cob or a pure lime-crete mix.

Does anyone have an opinion on this.

Should/can cement be avoided?

If you check out some of my other comments on Permies, you will see that I pretty much detest portland cement. Lime is a complement to adobe mixes no matter the type or recipe. Cement tends to trap moisture where you don't want it does not match the flexibility of the other building materials.

Among lime plasters advantages are that:

Lime is lighter than concrete.

Lime tends to be more locally sourced.

You can maintain lime plaster much more sustainable than concrete, which has a huge environmental footprint.

Lime plaster is like a steel and bends, (and self heals,) vs Portland Cement which is like aluminum will not bend but breaks.

The concrete industry and many contractors are the reason this product is so prevalent, which is changing as people become more aware of the environment and natural building practices.

Good Luck.

jay