Regarding targeting. It is more efficient for the advertiser, and potentially useful to the audience, when compared to non-targeted advertising. For example, an advert for Tampons on the side of a bus is already losing efficiency because perhaps only around 35% of the general population are females in that age group. On the other hand, online adverts can be targeted based on various factors. An advert on Steemit could be based on tags, so cameras might be advertised on the photography tag, far more efficient for the advertisers, and arguably less obtrusive to the audience.
This can also take the form of a product review which ends with a link to purchase the product. That approach is unobtrusive, highly targeted but the integrity of the blogger needs to be reinforced.
Yeah, I get why it's done, I'm just not much of a fan of advertising in general, haha. Targeted ads have never done anything for me, if/when I want something I find it myself. I don't like people telling me what to do, especially when those people are huge advertising firms who have been sponging up all my data just to try and sell my things I don't want and they don't care about.