When people use industry specific jargon and acronyms with someone not in their industry.
It is a very simple rule of writing and communication. You never just use an acronym out of nowhere, you write it out in full the first time and explain the acronym, and then after that you can use it.
Artificial diamonds can be made with a High Temperature, High Pressure (HTHP) process, or a …
Doctors, military folk, lawyers, and technical people of all variety are often awful at just throwing out an acronym or technical term that you literally have no way of knowing.
Usually though, I don’t think it’s a conscious effort to sound smart. Sometimes, it’s just people who are used to talking only with their coworkers / inner circle and just aren’t thinking about the fact that you don’t have the same context, sometimes it’s people who are feeling nervous / insecure and are subconsciously using fancy terms to sound more important, and sometimes it’s people using specific terminology to hide the fact that they don’t actually understand the concepts well enough to break them down simply.