People writing malicious software do these things. If its the ONLY way to truly get malware on millions of iOS devices, they will try their best at doing this.
Again, you are comparing this to big companies. The games I write for educational purposes are not rated by the ESRB. And if I want to do something like xCloud for my educational games, and I do not have the proper infrastructure in place to do it safely (just argument here, but even big companies can have breaches), bad things can happen.
Unless you think Apple should be able to play favorites, only allow game streaming from Microsoft because its Microsoft and Google because its Google?