As adverb, just means:
- very recently;
- barely; by little;
There are then cases where just can replaced with simply without to change meaning to the sentence.
As examples of usage of just the NOAD reports the following sentences:
That's just what I need.
You're a human being, just like everyone else.
Conditions were just as bad.
I've just seen the local paper.
I got here just after nine.
They were just interested in making money.
There also phrases where you need to use just, as in just about, just as well, just in case, just a minute; replace just with simply, and you get a phrase without sense.
The results obtained from Google don't mean that, as just appears more frequently than simply, just is more preferred. As the words are not synonyms, comparing them is like to compare the number of sentences containing house with the number of sentences containing moon.
With Google, then (as reported by other comments), you don't obtain results for English only, and you can obtain also results for phrases that are not grammatically correct.