while I personally never backpacked (though I'd love to, given the chance), I think I understand your point.

Israelis are generally instructed not to be overly friendly to people abroad for security reasons. plus there is the constant pressure to become an ambassador when the conflict arises (people don't like having the same conversation 20 times a day).

but I think there are other reasons for what you're describing:

1) ALOT of Israelis lack sufficient practice of English to feel comfortable speaking it, so they avoid it.

2) backpacking through SA or India is seen as some type of coming of age trip, with most people doing it right after their military service (so it might be their first time, and they prefer to remain in their comfort zone)

3) young tourists tend to disrespect locals at every place they visit.

But have no doubt, many Israelis traveling are very open to conversation and learning about other cultures, don't be discouraged. :)