I remember single-sided ~160kb disks, and I remember manually deleting DLL and EXE files in windows which I didn't need to save a space by the hundreds of KB when I was dealing with laptop drives in the tens of megabytes.

These days it just depends on how much media and other data you deal with, and how bad the software you deal with is. I have seen software bugs creating runaway temporary and log files running to the 10s of gigabytes.

(I've been guilty of writing software with a bug like that, although it did not get anywhere near customers before I fixed it.)

Disk sizes vary more than ever, too; the oldest useful laptops today, and some of the smallest new PCs/PC-based tablets have SSDs in the low tens of GB. The largest desktop drives are 4TB, and it's not that unusual to have 2-4 of them in a system.

(Let's not talk about servers; a few years ago 100TB directly attached to a single server -- as opposed to as the total capacity of a SAN -- was unthinkable, whereas it's merely a little unusual today.)