The downside is that a majority will have to pay higher overall fees for the benefit of a minority (those travelling regularly aboard)

I am 99% sure that for most of the phone companies a call in a home country and outside of it costs the same. Especially, for companies with subsidiaries all over the world such as vodafone and tmobile

Scaled across millions of people the difference will be next to nothing. They're inflating the prices exponentially because "everyone else is doing it".

Making SMS "free" didn't make plan prices go up.