Voice-controlled assistants are having a moment. But there may be an intriguing wrinkle that their makers have to smooth out: users don’t seem to be using many apps.

The number of Skills—the Amazon name for apps that operate on its Alexa smart assistant software—available for the company's Echo smart speaker have risen significantly in the past six months, from 950 last May to over 8,000 today. But an analysis of the way people use Alexa and and Google’s Assistant platforms shows that third-party apps aren't too well used, nor particularly sticky.

The analysis, which was carried out voice software startup Voice Labs, shows that most app don’t get any user reviews, which suggests they’re not very popular. And of all the people that start using an Alexa or Assistant app, only an average of 3 percent will still be using it a week later.

People love smart assistants, like the one built into Google's Home speaker. But they may not be making full use of all the software they can offer.

For anyone that has an Amazon Echo or Google Home speaker in their place, that may not come as a huge surprise. As with all new consumer technology, home assistants are at first a novelty but quickly become a functional part of the home—being used to play music, set timers, make shopping lists, and so on.

But users will also know that the few push notifications that Alexa and Assistant provide are obtrusive—which is, presumably, why they don’t use them very often. And because there’s no visual cue to remind users that there’s an "app for that" on their home assistant, it’s incredibly easy to forget that a niche task can be performed by simply speaking aloud. It's understandable, then, that people either don’t bother to use, or quickly forget about, most third-party apps on these pieces of hardware.

Whether that’s troubling or not depends on the strategy that the likes of Amazon and Google are hoping to pursue. If the idea is for Alexa and Assistant to become voice assistant operating systems—on which other developers build the bulk of available functionality and software, like Apple’s iOS and Google’s Android—it could be a problem.

Amazon, of course, already knows that, even if it isn’t publicly airing a solution. After all, it has vast quantities of data from Alexa devices that it mines to improve the services provided by its voice assistant.

That could be why it’s reportedly toying with the idea of adding a touch screen to the next iteration of its Echo smart speaker. While it may seem like a strange idea to add a screen to a device that’s all about voice command, it would also improve discovery and make it possible to add in unobtrusive push notifications. And that might just get people using their home assistants for more than music and cooking timers.

(Read more: Recode, Bloomberg, “In 2016, AI Home Assistants Won Our Hearts,” “Alexa May Have Won CES, But It Still Has a Fight Ahead,” “Alexa Gives Amazon a Powerful Data Advantage”)