Why are AC adapters (wall warts) designed to block adjacent AC outlets?

The AC adapters for a lot of equipment seem to be specifically designed to block the AC outlets around it (this is in the US).

Is this a safety feature to minimize the power to that outlet or just lack of common courtesy?

Clarification: I am NOT asking how to "fix" the problem, but why it exists in the first place. Most of the fixes comprise of adding more wires to a problem which I don't understand why it exists in the first place.

NB! Question is not - What is an AC adapter? There sure is bad/lazy design out there but some adapters seem to be

"specifically designed to block the AC outlets around it"

. Why would that be? Since

"There is no need to limit the current from the output, as most such devices handle low power levels, if compared to an iron or a room heater."

Please see the attached picture of the AC adapter with "ears" to prevent the use of nearby outlets: