Steal has become relatively more popular over time although the difference is probably not large enough to attach a lot of significance to it.

https://books.google.com/ngrams/graph?content=rob%2C+steal&y...

If I had to guess why (other than reasons...) I'd probably speculate that steal tends to have a broader meaning while rob is more likely to be applied to physically robbing someone.

Interesting, playing around with that shows it's a lot tighter in Britain - where it's also the other way around in the past tense by quite a margin. (Likewise in the USA until recently.)

I'm British, so maybe that explains my initial confusion.

Comparing the past tenses is probably more appropriate as that's the tense that those verbs are most commonly used in. It also occurs to me that a lot of the use of just "rob" may well be the name "Rob." Given that, the usage of stole vs. robbed tracks quite closely with just a bit of an upward track of stole over the past couple of decades.

I originally thought that rob vs. steal might be one of those Germanic vs. French roots thing but both words seem to be traceable through Old English.

> a lot of the use of just "rob" may well be the name "Rob."

Google ngram search is case-sensitive though, so that's unlikely to account for much - and probably offset by sentences beginning with the verb, e.g. 'Rob him, quick!' said the man.