In the current Android interfaces of Xiaomi there are "recommendations" which are nothing more than advertisements - fortunately they can be turned off, which will be briefly described in this article.
Xiaomi makes every effort to ensure that the ads or recommendations can be disabled, but does not make it too easy for the user. At least that's still the case, and it can be assumed that Xiaomi will continue on this path.
The English-language website androidauthority.com has dedicated a longer article to the topic by Background of the MIUI-Ads explained will be. In short, Xiaomi justifies the surface advertising with the low price of the devices.
If advertisements are played in an app or apps are recommended for download in a folder, you can adjust this in the respective settings (via the gear wheel).
Whether it is good for the reputation of the Chinese brand that potentially tracking advertisements are integrated into the interface - because for all recommendations or advertisements, data is transferred to an external server.
It is also possible that advertisements transfer data to third parties that the user has not released - if an advertisement runs with the rights of an app, this can have far-reaching consequences for the security of the data.
From Xiaomi's perspective, the displays are a way to increase the margin per device. Unlike margin-primus Apple, Xiaomi is only supposed to earn less US dollars per device - any way to increase profits is of course fine, even if it means putting the customer's data at risk.
Another is pursued by Amazon, where products with advertising are slightly cheaper to buy than, for example, the ad-free Kindle. Here the customer has the choice, at Xiaomi they apparently assume that in the end you will earn more if you display the advertising for everyone and hide the option to deactivate as well as possible.
Update: also updates for MIUI 10 have not brought any further advertisement so far and the possibilities for deactivation are still available.