Is there a mod for the sims 1 that has sims NOT change thier clothing when they go to work?

I don't know of an existing mod that does that, since most players enjoy seeing the job outfits, but it would be easy to make one yourself.

What outfit the sims wear to work is controlled by the work outfits listed in the Work.iff file. You can use Career Creator 3 to eliminate those outfits in whichever careers you wish. Career Creator 3 is a lot easier to use than some of the other Sims 1 programs, so even if you're not a modder, you can do this.

You can get Career Creator 3 from this page at Sim Echoes. (Sim Echoes is sometimes slow, but the link IS still good, so if it doesn't work the first time you try it, try again in a few minutes.)

Career Creator 3 comes with lots of helpful information, which is in a folder called Docs once you install the program. But really, all you have to do is to make the job outfit fields blank, and your sim will go to work in whatever they usually wear.