For my part, I used to be an active member of a political party that while completely legal and not advocating anything illegal, due to its position on the far left meant that a lot of people I associated with used to be under surveillance by the Norwegian security services, and many of them were denied entry into the US for years and years.

At the time I was involved, it was less controversial, and so I might have "escaped" surveillance, but I regularly met people who were more than once taunted on open streets by high level people in the security service who'd joke about personal details of their life that they had obtained through surveillance that in no way were relevant to the security services (e.g. asking about the fight some guy had with his wife the previous night).

There are plenty of people today that are in close enough proximity to the types of people and groups who are the subject of security services interests these days that would have every reason to assume that their conversations with their mothers would be monitored just because of either who they are, or who their friends are, or even because of the groups their friend peripherially belongs to.

It's not a situation that is particularly fun to be in, and I understand very well why third parties in situations like that would prefer not to have to think about whether or not someone is listening in for their own gratification.