I should have said "C: drive"/"HDA1" but wrote boot media so I could save having to think about my phrasing. I meant that's where you would install anything that is primary to your workflow and might read and write lots of files, because that's how it was programmed, git, your ide, compiler, test suites, database, webserver and log files, or whatever programs you create and handle your workspace with, whatever that may be (photoshop, design software, etc).
the point is, things you would never risk not having on permanent storage, and which are written with the expectation that they will be. if it's ironclad (six/seven sigma, and backed up to real permanent storage behind the scenes in case worse comes to worst), you wouldn't have to give up this abstraction. it would still be a hard drive and not, you know, the current contents of your ram since you booted.