It's a great question. TouchDesigner and similar programs have a limited number of data types even though touch designer does a great job at being a little more general than other programs. Also TouchDesigner and Houdini both have shader languages that allow someone to make nodes that do general purpose array transformations which ups their utility a lot.
One big aspect is handling state. Connecting nodes without side effects is great when each frame is a cycle and all you have to do is transform data into a final result. When actual state is involved it becomes hacky or impossible to do in with only transformations. Other similar hurdles are branching and IO.
The other is having general purpose programming underneath. Shader languages enable a lot, but using a real programming language like C++ somewhere not only opens the door to whatever you need, but allows you to integrate all the libraries already made as well as call out to OS IO APIs etc.
It is amazing though how nice it is to work with an integrated and fluid environment where iterations are updated in real time and errors are narrowed down for you, not to mention profiling broken down by node.
One big aspect is handling state. Connecting nodes without side effects is great when each frame is a cycle and all you have to do is transform data into a final result. When actual state is involved it becomes hacky or impossible to do in with only transformations. Other similar hurdles are branching and IO.
The other is having general purpose programming underneath. Shader languages enable a lot, but using a real programming language like C++ somewhere not only opens the door to whatever you need, but allows you to integrate all the libraries already made as well as call out to OS IO APIs etc.
It is amazing though how nice it is to work with an integrated and fluid environment where iterations are updated in real time and errors are narrowed down for you, not to mention profiling broken down by node.