Well in the end modern smartphones are just general purpose computers which have some artificial restrictions on what you can do with them and happen to have a

Well in the end modern smartphones are just general purpose computers which have some artificial restrictions on what you can do with them and happen to have a touchscreen/modem/speaker/microphone etc. So the dieler just being a app is a direct consequence from smartphones not being any kind of "special/magical" embedded device. Through silently overriding the Dialer with a program I would normally suspect to be malware which sneaked on my phone is a horrible think to do...