Amazon has introduced a change to the policies that Alexa Skills developers have to adhere to, banning advertisement from any and all facets of Alexa development except music streaming and radio services, as well as "flash briefings" or small, pre-recorded segments from news broadcasters and the like. This means that Skills that don't use those features cannot have any advertising in them at all, making it a bit harder for Alexa Skills developers to monetize their creations. The change was made without any fanfare, and Amazon has yet to announce a replacement monetization method for developers.
Developers have already been banned from having visual advertising in the Alexa app's Home cards for Alexa Skills, making audio ads the last bastion of monetization for Skills that weren't based on money management in some way, and even those couldn't use Alexa's built-in voice. The policy regarding money-centric Skills, however, essentially states that a Skill cannot ask a user for donations, cannot recommend other Skills or a separate app on the Skill store, and cannot offer compensation of any sort for completing an action. According to recent speculation, Amazon might be introducing integration with Amazon Payments in some form to help developers monetize the Skills that they build for Alexa to compensate for its latest policy change.
While Alexa Skills developers may now have issues with making money from the time spent developing services for Amazon's AI assistant, the reason for Amazon's tepid attitude toward advertising isn't hard to see. Advertising can still be used during flash briefings and while streaming radio and music. Essentially, this means that advertising is still allowed in content delivery Skills. Doing things any other way could invite serious backlash from consumers, and risk Alexa and the Echo's status as a top-tier consumer voice assistant. Google Home proved this not too long ago, when consumers got up in arms about their units trying to coax them to head to theaters and see Beauty and the Beast, then shortly after, when their devices were hijacked by a clever Burger King ad that forced them to advertise the Whopper Burger.