The other problem is that "good" ads almost inevitably devolve towards "bad" ads as there is always incremental profit to be made from making your ads more intrusive while the cost to the brand/product is hard to quantify until one day a competitor comes along and eats your lunch.

Edit: One thing that became clear to me recently is that relevant ads do not maximize profitability. A market where ads are less relevant has more ad placement inventory because high-margin "irrelevant" advertising can be placed in front of more people.

For example, I've never expressed an interest in gambling, poker, or casinos. But those businesses have more money to advertise so I see their ads anyways. An ad platform is not going to leave money on the table from these advertisers just because they're "not relevant" to me.