I don’t know a lot about the rest of Europe on this, but here in France it’s been more than a decade SMS are unlimited in mobile plans, and these plans are quite cheap.
We also have free roaming in the whole Europe.
We also have free roaming in the whole Europe.
The adoption of messaging apps caused a lot of carriers to reduce or eliminate the SMS fees, as they saw the business was evaporating.
One of Signal's main cost centers is activation SMS messages. For many other small players it is a significant factor too.