Because people wanted to take them around. At first, I think the dev system fit in 16 gig macbook pro without any trouble and it was a startup, so it was just natural to say that's all you need. Then the dev env started getting a little bit bigger.

I showed up at the company and noticed you couldn't run the vm for a test and compile separately at the same time. Next I found out I couldn't have a bunch of tabs open while doing dev. So that was painful, and I got a desktop. The existing people who were used to how things worked said you shouldn't have a bunch of tabs open, don't do that and it works fine (oh and don't run any tests while compiling).

Then as memory use kept up even the at most 4 tabs people found they kept running out of memory and they bought a few 32 gig laptops and suddenly things worked again.

A few of us have desktops, most people are struggling with 16 gig notebooks and they started buying 32 gig notebooks for people that want them.