[midoridensha]

>Advertising and propaganda have always been the exact same thing

They're really not, though they are similar in many ways. They have different connotations: advertising is done generally by for-profit companies trying to sell stuff and make money, while propaganda is generally done by governments trying to shift or control public opinion. We have different words for these things for a good reason.

[carlosjobim]

But is there really a good reason? The only difference is that one tries to make you buy something and the other tries to make you do something. It works in the same way, an entity trying to propagate their agenda.

[midoridensha]

Yes, there's a good reason, because those two things are different, as you yourself point out. Different words for different things.