Poorly, in most cases, via various flavors of JavaScript and derived frameworks therein. Sometimes with additional overhead referred to as "targeting" which gives a worse outcome and user experience, regardless, over simpler implementations that serve to inform. Targeting forgets causality, typically.
Next comes YELLING-LOUDLY-TO-COME-DOWN-TO-THE-LOCAL-CAR-DEALERSHIP-FOR-NO-MONEY-DOWN-OFFERS phase of advertisements, which type are also routinely and nearly uniformly ignored.
Sounds like you should start a trillion dollar ad business! Or if you're worried about ethics start a "niche" billion dollar ad business that only serves ethical ads!
Next comes YELLING-LOUDLY-TO-COME-DOWN-TO-THE-LOCAL-CAR-DEALERSHIP-FOR-NO-MONEY-DOWN-OFFERS phase of advertisements, which type are also routinely and nearly uniformly ignored.