In the GRE, why are we allowed to use calculators and not dictionaries? Basic arithmetic is pretty trivial, but it can take time and is often very tedious for large quantities and so they allow us to use calculators when writing the GRE (Graduate Records Examination).

But shouldn't we be allowed to use dictionaries, memorizing plenty of words is pretty trivial too, and is tedious. I get that it helps improve our vocabulary, but like we use calculators when doing large calculations, we can simply pull out a dictionary when we see a new word right?

Is it because we save time by knowing the word already? GRE tests several other things including sentence structure, meaning, context etc... But wouldn't it be better if they left vocabulary off that list of things they test?
The GRE is ran by ETS, so only they will be able to answer your question about why they don't allow dictionaries.

Your same logic starts to question the entire point of these tests. Using Google is trivial and is engrained in our day to day lives, so why can't we use it on the tests?