It’s not just time and resources, they too are being lied to. If the scam is good enough that people will fall for it, some advertisers will as well.
Right now there are no regulations, so many don’t care at all. That sucks, but the scammers are the problem here. They are the ones trying to rip you off. The ad companies might not care if you get screwed or not, but it’s unrealistic for us to expect them to know EXACTLY what every client’s intentions are. A business could run legitimately for years and then start running a scam. How long would we give the advertisers to realize that the client has started scamming people? Do they get in trouble because they ran ads for someone who would LATER start scamming people?
I’m all for discussing other ways to control advertising, but shooting the messenger isn’t it.