In the earliest days Java was this thing that showed up in your browser and caused it to just wedge hard (blocking the UI, even) until things got started any time someone decided to embed an applet in a page. Since some people were using it to do all kinds of stupid things (animated fire, anyone?), you could run into it at any point with no warning.

It was ugly. It had terrible looking widgets that were out of place on Windows, Macs, AND Unix boxes - quite a feat at that.

One (dumb) thing JavaScript had going for it was that at least initially, you had to have it on to get CSS action on pages in Netscape. If you turned off JS, then you lost CSS too and things probably looked pretty ugly.

I want to say that some browsers forced you to keep JS on in order to parse a proxy.pac and those of us in corporate/educational environments with filtering proxies had to deal with that, too. Add it to the CSS issue and now you have multiple reasons to leave it on and try working with it. By way of comparison, you could get by with Java disabled.

I still ran with both off in the bad old days and took the lumps, but I'm just cranky that way. I still run with JS off by default.