Firstly, you can more easily lose your mobile devices (by absent-mindedness), much more easily compare to laptops due to smaller size of mobile devices.
Secondly, most of people don't pay too much attention on security of their mobile devices (AV softwares).
Thirdly, when phones broken technically, you are nearly not be able to fix it yourself, and have to bring them to Maintenance Officies. It is another risks. With computers, people can fix issues themselves, or at least don't leave important data to others.
I only dedicate very small funds on mobile devices, and most of time, wallets are empty. Whenever I hang out and have plans to do something, I send a few bitcoin to mobile wallet, just in case in need to use it with urgent need.
Yes the growth of crypto apps on mobile phones are good development but what phone manufacturers are doing are not making any much impact for several reasons based on my evaluation.
1. There are several trusted third party app developers that have made their software open for download on either playstore or AppStore which over the years have become trusted by people. So, I don't see any crypto enthusiast who will buy a particular brand of phone simply because it has inbuilt crypto wallet. What about the support or private key security that is germane to any wallet holder.
2. Now for those new people buying those brands that we might think seeing the crypto app on their phones can lead to their curiosity which might then push them to crypto. Today, I have seen several apps on phones that serve no interest to the users because he does not understand its functions which could have been deleted if there is a way. So, without understanding of what crypto is all about, the app will be fully useless.