Ask HN: How can advertisements be better?

I personally envision a day where advertisements are both relevant and of immediate use to users. Instead of "HEY LOOK BUY THIS!" they function as useful reminders, suggesting we purchase goods that are of personalized use to us.

What do you all think is limiting advertisements (across all mediums) from achieving this? Is this even possible? Will ads forever be necessary evils used to finance freemium businesses and Google?