This is true, but parallel programs are not more limited - they're just good at different things. We will write different kinds of programs to do different kind

This is true, but parallel programs are not more limited - they're just good at different things. We will write different kinds of programs to do different kinds of tasks because of access to massive parallel compute. Parallelism allows you to do computations that integrate huge amounts of information, like checking every pixel of an image against thousands of weak rules all at once. This is very inefficient to do serially because you can only check one at a time. It's also a huge usecase right now because machine learning lets you learn weak rules from data.