Mobile games like Fortnite for Apple iOS can become very popular because of their interesting gameplay, and good storyline, so most people maybe more likely to download more 3rd party mobile games than apps . There are also not any 1st-party mobile games which are released by Google and Apple.
I feel most people usually stick to using the 1st party apps like Google Chrome, Google Drive, Apple Safari, iTunes, Google Play, Calculator, etc which comes pre-installed on their smartphone or tablet because most 1st party apps are good enough for most users needs, and many users maybe too lazy or don't know how to look for 3rd-party apps.
I'm usually fine using most 1st-party apps like Google Chrome, YouTube, Dialer, Hangouts, Contacts, etc which came with Google Android where I am fine using only 1st party apps.
But, the 1st social networking and blogging apps like Google Plus, Blogger/Blogspot, etc for Android are not as good because the social networks don't have the content which I want to view, or none of my friends uses Google owned social networks except YouTube.
I want to see what it is like to play a 3rd-party game like Clash of Clans, Asphalt 8, Pokemon Go, Temple Run, Subway surfer, etc. I usually give popular 3rd party games a try to see why they have such a large fan base, play with friends, and to see if the game is worth playing for a few minutes a day.
I agree, I think it is depends on the brand/owner of the operating system. I think Windows Phone and Blackberry OS phone users are more likely to look for third party apps because the apps which come with their OS are not as popular as Google Chrome which comes pre-installed in most Android phones.
Some iPhone users may stick to using 1st party apps because they are huge fans of iPhone and rather use Apps like Apple Safari, iTunes, Apple Music, Apple Maps and other 1st party apps which are made by Apple for iOS. Some Apple users may prefer not to use Apps made by Google, Amazon and Microsoft because they are not fans of non-Apple apps.
