Propane is much easier to use than LNG (which is mostly methane) as it remains liquid at ordinary outdoor temperatures with relatively moderate pressure.

Oh, you are right, I should be more specific, I intend to refer to the practice of bulk transport of atmospheric pressure LNG at globalized scale.

Propane is a refined, and somewhat synthesized molecule. LNG is rather raw, and contains a lot of free hydrogen, methane, and sometimes other contaminants like sulphur (though that is mostly lower grades).

Think of the difference between 91 octane gas at a pump vs slightly filtered crude oil.

Propane is a completely different molecule from LNG which is mostly methane. Methane is not liquid at normal surface temperatures even at high pressure; propane is.