Besides all other things people have mentioned there is also new requirements for ui:s. People complain if their drag-movement with a finger don't align perfectly with a nice animation on the screen on a cheap phone. Those things did not exist 10 years ago or 20 years ago. Interfaces were simpler and easier to build and users were happy that it worked.
But I do agree that software could be a bit faster nowdays.
But I do agree that software could be a bit faster nowdays.