Say you paid for your ad to be in a magazine. The distribution had roughly 600,000 subscribers that were “guaranteed” to get the magazine. That’s great, if you’re the publisher. With this type of advertising you can never be guaranteed to have someone buy something based off of your ad. Let alone see your ad at all. And if they did, you may never know the source of purchase.
With PPC Campaigns when someone clicks, visits your website or just sees your ad even if they don’t convert you can remarket to them, say with a display campaign. This isn’t doable with traditional media.