Olive oil (pomace) is one of the ingredients I use in formulations. Olive oil is very moisturizing, but doesn't lather at all, and it renders a very soft bar of soap. Tallow and palm are both hard, stable lather-building ingredients.

In short, olive oil and palm oil are not really comparable. They would both be best used in some combination to yield a product with both moisturizing and lathering qualities.

Is lathering important for any particular reason?

I've been using castile soap for a while now, and, while it's true that it doesn't lather as much as some other soaps, that's never really bothered me.

It ultimately depends on the person using it.

Lather is often associated with a soap's cleansing qualities, which is usually desirable. But some people prefer their soap to be more moisturizing than cleansing.

I personally find pure castile soap to be too moisturizing and not cleansing enough. I prefer a more balanced soap with a bit of both qualities.

Does it actually make the soap more cleansing, or is it just a perception thing?

My understanding was that, when companies add lathering agents to their products, it's the same as dyes and fragrances: really just there for cosmetic purposes.

Surfactant types and levels are different from different ingredients. That's what does the "cleansing" you're asking about. Not all oils and fats clean the same way. Some are better for different "messes" than others. Like wood ash makes a fantastic soap to strip grease. However, it also dries the hell out of your skin and can lead to lots of cracking.

It's all a balancing act as to how strong of a soap you want compared to damaging.

I've been using this 100% olive oil (fat-wise) soap for several years, it doesn't lather quite as well as other soaps i've used but it does the job well enough:

https://www.hollandandbarrett.com/shop/product/oliva-pure-ol...

I'll have to give that a try, I used to use the Kiss My Face 100% olive oil bars before they shut down and were acquired, now their products are awful.

I've been using this [0] as a replacement which has been good but the Laurel blend seems to dry my skin more than the straight olive oil KMF bars did.

[0] https://www.amazon.com/Aleppo-Soap-Hand-made-All-Natural-12-...

Traditionally, castile soap is 100% olive-oil based. It's often sold as liquid soap, to eliminate any disadvantages of the softness that olive oil gives to solid bar soap.

Thanks friend - I sort of assumed it was something along those lines but was curious about your thoughts as a pro.

Olive oil gives you very soft soaps, (hydrogenated) palm oil and beef tallow give you very hard soaps.

hence palmolive, presumably? Somewhere in between?

Hah, never made that connection.

But yeah presumably.