I can say that people in Israel prefer facebook groups for many reasons:

1. It allows for "team search". My friends knew I'm looking, so they tagged me in relevant posts they saw. Can't do it anywhere else (including marketplace by facebook themselves)

2. It allows for group communication with the publisher of the post. One asks - everybody sees.

3. It gives a sense of power to those who seek to rent. Many posts with high prices have comments like "You are crazy", "You are a pig", "whoever pays this much is as sucker". It almost warms the heart, we fight the greedy landlords. It almost make it fun, like a witch hunt.

As a landlord though, what’s the reason to use Facebook then? Is there no alternative like craigslist in Israel?

I’ve only seen posts of apartments for rent in Facebook groups that are aimed at college students. (In the US)

Otherwise, Craigslist is basically king.

Young people use facebook to find apartments.

So if your apartments target young couples or room mates, facebook is your place. For families we have craiglist-like solutions.

A Facebook group is the primary source for advertising rental properties in Juneau, AK. Just a normal group, not the marketplace.

Ditto Helsinki, Finland:

https://www.facebook.com/groups/235368102105

I listed my rental flat a bunch of places before using the group, since I started using it I'd not look elsewhere.

FB buying/selling groups (particularly for housing) are quite common I'd say. In my experience, you will generally find them categorized as part of a college or university (e.g. "San Jose State University (SJSU) Housing"), but a quick search for "Bay Area housing" also results in numerous such groups.

typical at college campuses in the us