Social Messaging and the decline of mobile phone numbers?

Does it have any meaning that on my website, I only provide contact details for social media, and not my mobile phone? 

In my primary job at present, I get to see and hear a lot of customers discussing weekend plans and how they're arranging to meet up. I hear a lot about Facebook, Twitter, Viber, WhatsApp. But I'm rarely hearing people ask for anyone's phone number so they can SMS (which also has an impact on iMessage for that matter).

With promotions such as last weekend's Vodafone free international calls and texts offer, is it as relevant as much anymore to have this (or do people already message internationally daily using other services such as Skype, Whatsapp, etc etc)? I'm genuinely intrigued from my previous work in this role, and how it impacts on Mobile Operators.

Is it a bubble I'm in? Are you noticing less people contacting you first through phone and more likely through another medium such as Facebook, Twitter, LinkedIn (of which I meet many others also)? Or is it more a case that these have become a supplement to to text message and voice calls (although the latter of those is on the decline also).

At one point, I suspected that Text Message would stay the primary means for personal communications to your nearest loved ones. Something isolated from all other means of communications meaning it was perfectly private. However, there is no guarantee on this so I'm intrigued to hear people's thoughts on this.