You're obviously not the only one who deactivates javascript by default, but a quick google brought up numbers of around 1% for users with javascript deactivated. I can see why a lot of developers wouldn't be too concerned about that 1%.
So there was once a definite use case for supporting them in a B2C context, at least. You still see it in .edu/.gov/.mil quite a bit as a requirement (Sec 508, et al).
Here is a source for the 1%: https://gds.blog.gov.uk/2013/10/21/how-many-people-are-missi...
EVERYONE has javascript disabled until the js payload is downloaded. Which is extremely important on high-latency or slow network connections.