Because it's warranted.
An extreme example, but as a new reader, I can see why some would be turned off. I'm around page 60 and it's getting easier, but it's a legitimate complaint IMO.
Using made-up* names for things that do no exists is perfectly normal in scifi and fantasy. I see nothing difficult about that, and there are "worse" examples than Dune.
Most of them end up being explained, or are obvious from the context (or at least when there's enough context).
Sometimes fiction does this badly of course. TV Tropes calls this "Calling a rabbit smeerp", where a smeerp is a thing that is just like a rabbit so the name is pointless. But most Dune's words either describe something that does not have a real (or English) equivalent, or to make the created world feel more real, by having it have its own customs, words and things.
One thing why i love Dune so much, many scifi worlds feel incredibly shallow.
Heck, sometimes real words are used confusingly, like The Force in Star Wars, which does not refer to force but is essentially magic. (Might be an example of that trope i mentioned above.)
*Funny thing about Dune's words is that they're based on real terms, evolution of language in-universe. For example, Kwisatz Haderach comes from Hebrew, and indeed does have similar meaning. Which is unusual for scifi in my experience, usually new words etc. have nothing to do with real things... (Though of course you find out about these only outside the book itself.)
Also funny thing about the Landsraad (in Dune, it is like a senate or parliament) as i notice you had it circled:
It took my ages to see why it would be an odd word for English speakers... because the word "raad" has a form in Finnish, "raati" (meaning council or jury or such, depending on the context), it was obvious for me. The problem was that i didn't realize there is no such term in English.