One word: convenience. You can do object oriented programming in C, so one does not "need" C++? moc allowed a nice syntax for signal and slot (invented at a ti

One word: convenience. You can do object oriented programming in C, so one does not "need" C++? moc allowed a nice syntax for signal and slot (invented at a time in which C++ compilers did not support templates). And now it allows QML. The disadvantages are not as bad as one claims. It's not so hard to integrate moc in any build system.