In my experience it doesn't do much. For example, I made the mistake of contributing to the campaign of a politician. Now I get texts from candidates all over the country. If I reply STOP to one, I just get sent more texts from another number, for another candidate in another state. I just got tired of replying with STOP after the 20th time. This just guarantees I'm never giving any money to any candidate ever again.
They sold it to a liberal political group, who then sold it to an extreme liberal group.
I get dozens, sometimes hundreds, of spam emails, every day, with the most batshit insane messages. It’s especially bad, now, with the US election coming up. The one saving grace, is that it wasn’t a right-wing group. They make the ultra-liberals look like a bunch of teetotalers.
Since she used the iCloud.com variant of the address, I simply nuke all emails that specify that, as a destination. Apple won’t let me block the domain, so I have to apply the rules, after they fill my inbox.
Sometime in there, one of the spammers figured out that icloud.com will also receive iMessage texts, so they have started coming to that, as well (so far, it is from legit political groups. I don’t expect that to last). I delete and report as junk. I very rarely respond with STOP.