Because certain types of political messaging would be highly effective if carefully targeted, but would be a massive scandal if they became more publicly known.

So, the problem with targeted calls isn't the unsolicited communication, but that if politicians could send customized messages, they might sometimes send evil ones?

Not even necessarily evil, but it allows you to promise everything to everyone without being easily called out on it.

It is 2 different problems but if a call in unsolicited and political, it could have great consequences if they are micro-targeting millions of Americans.