as long as someone getting ahold of your app PIN can’t hijack your account or pay money out to an account in his name, where is the risk?
Oh dear … the above naive undersatnding of security is what leads to easy theft. There is a reason why most banks and eMoney institutions use strong passwords, pins and 2FA (Revolut is a fairly shocking counterexample). You should read about Kevin Mitnick, or the many breaches and thefts performed by folks who obtained only basic account information, e.g. http://news.bbc.co.uk/1/hi/entertainment/7174760.stm
Someone would also have to get ahold of your phone.
That’s why apps allowing money transfers on phones (paypal, transferwise, bank mobile clients, etc) have better security than Revolut …