UK mobile data is filtered by default, while fixed-line isn't. I suspect this is an artifact of "adult" premium rate phone lines - access to those numbers must

UK mobile data is filtered by default, while fixed-line isn't. I suspect this is an artifact of "adult" premium rate phone lines - access to those numbers must be limited to those verified to be over 18, and while I've not done the research to back this up it wouldn't surprise me at all if it's the application of this rule over the years that has led to this situation. Of course a mobile telephony provider is going to be a lot more certain which phone numbers attract the specific premium rate categories to need to be blocked than they are which random domains should be blocked :P.