But you have options. I leave all my stuff in the cloud, and have a 4 TB drive (portable hard drive) for all my iTunes moves so 128gb computer works for me going to and from work. I keep my 4 TB drive in my computer bag and pull it out when I need it, which is usually only when I don't have strong enough Wi-Fi to stream.
This is a solid, viable option - and frankly, one I have to embrace and transfer to myself. I'm a classic gotta-have-it-all-with-me-all-the-time guy. So the SSD for space, speed and reliability all internal is very appealing to me.