Obviously, not all the traditional locally installed applications, like Photoshop and Microsoft Office have equivalent online apps. But the development of online, web based apps, is moving rapidly and as of now there are apps for creating and handling documents, photos, images and even videos that offers most of the functions that most of us would ever need. And as time goes by, they will only grow more numerous, capable and powerful.
We could still use a traditional PC to access the Internet and connect with all those new and exciting web based apps, but PCs are not configure and optimized for that. Personal Computers are best used to run local applications where we, the end users, need to keep configuring and optimizing them for whatever task we are running. Even more, PCs need lots of maintenance. Over time, a PC used to access the Internet will get slow, infected with viruses and loaded with documentation and data that may be lost whenever the PC starts to misbehave.