Apple founder Steve Jobs first tried to sell the idea of the podcast, which is a long-form digital audio show, in 2005, and the format was integrated into iTunes. Podcasts experienced slow growth, but finally exploded in 2014 thanks to the blockbuster success of the true-crime series Serial. One in five Americans now listens to a podcast each month, and some shows now generate millions of advertising dollars as podcast networks are attracting venture capital.

Get Data Sheet, Fortune’s technology newsletter.

But the New York Times reports that many podcasters feel Apple (AAPL) isn’t responding fast enough to that growth and continues to treat podcasting as a “free feature to help the company sell hardware.”

In particular, podcasters speaking to the Times were frustrated that promotion channels within Apple’s ecosystem were narrow, that they were given access to too little data on their listeners, and that iTunes’ social media features were cumbersome. iTunes also limits revenue for both podcasters and Apple itself, because it does not allow for paid episode downloads or subscriptions.

Competitors are poised to take advantage of iTunes’ shortcomings, with Google (GOOGL) and Spotify rolling out new services to host and distribute podcasts. Individual podcasters and growing podcast networks, such as Gimlet, NPR, and Marc Maron’s WTF, are creating their own distribution channels, usually standalone apps. The podcast tracking service RawVoice tells the Times that Apple’s share of podcast listenership is down from 70% to 65% since this time last year.

For more on Apple, watch our video.

That decline, and missing the revenue from a growing industry, looks particularly significant in light of Apple’s current struggles to stay appealing to investors, which have led CEO Tim Cook to focus attention on content and service revenues.