@Cathy17
Well, airbnb may not suit everybody and there are other platforms to list your property.
What if your potential guest has a poor command of spoken English, but the written English is ok - would it still be useful to talk on the phone ? What about those who do not even speak English but are still able to make a booking on-line and are using google translate to communicate in writing. Sure, something could get lost in translation, but when the end is good all is good ? Or not ?
Unless you are off directory, revealing your phone number to a potential guest could also reveal your full address from the phone directory and would not be entirely safe. There are scammers out there.