Just by guessing, I would say whatsapp/FB/instagram/Snapchat/youtube are the most browsed apps. All those apps use Neural Networks in the background, for text translation, automatic subtitles, picture and video filters, encoding, decoding, upscaling video, ...

Neural networks will run constantly in the background to analyze phone sensors data and adjust the device energy usage, infer location, etc

Even games will use them massively (see the RTX application from Nvdia)

A performant single threaded CPU can probably run those AI applications fine, but an AI coprocessor (or neural processor or DSP or whatever the marketing named it) runs those applications by using 10 times less energy (easily)

I recommend to everyone to take a look at http://ai-benchmark.com/ . The improvement in this domain is massive, like an order magnitude bigger over the last 2 years, to the contrary of CPU and single threaded performance

Edit : oh I also forgot mandatory usage of NN for facial recognition and pose recognition. Regarding sensor, the new radar in the Pixel cannot work without neural network : https://ai.googleblog.com/2020/03/soli-radar-based-perceptio...