system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Why are there no junk howlers?

Howlers seem to be used solely to shame people in Harry Potter, but their much more obvious (and often, moral) use would be advertising. Even if it's illegal, that doesn't stop scam spam filling people's inboxes. If the issue is that it's towards a crowd, making illegal/dodgy advertising harder to get away with, then howlers could be limited to propaganda; spreading misinformation (or even true information) about commercial or political competitors, without any clear affiliation or even affiliation at all with those its trying to help.
gpt
There’s no point to them. Junk mail needs to reach millions of homes- the 1 person who responds to the ad covers the cost of the 99,999 people who chuck it in the bin without even looking.

The population of Magical Britain is small, and tightly interwoven by marriage and shared experience (work, school, etc.) You can’t run a business by alienating 99% of your market to zero in on the 1% who might place an order. Instead, you place ads in high profile areas where the vast majority of wizards end up like Diagon Alley or Hogsmeade, and networking by word of mouth.