Why polyester work pants?

I just bought some pants to wear for vehicle projects, and I wonder why they are 65% polyester. I would guess durabilitly or possibly stain repelling, seeing that my cotton pants can never be cleaned of the epoxy, oil, and paint I’ve spilled on them (the paint having hardened and cracked, making into holes at my knees). But trying on these new pants for just a short time, I feel they are too hot and stiff.

Fabric gurus, please teach me a thing or two about materials and their applications (and whether I should wear my new polyester pants or stick with cotton, if you have any advice).

Thanks.

Just based on my own experience, cotton is comfortable to wear while polyester makes me feel clammy and hot. But polyester releases some stains better than cotton, so will probably clean up better.

My choice is comfort first. I’d say go with the cotton!

Polyester clothing costs less than equivalent cotton clothing. It is more wrinkle resistant. Some people don’t seem to mind it, and some probably need to choose the lowest-priced item available.

I find polyester and polyester blends to be awful compared to natural fiber apparel. I wouldn’t wear it if it were given to me, much less spend money on it. But it is functional, and the matter comes down to personal preference.

Another vote for cotton. If you are worried about clean, you can get scotch guard and like that. I’d rather not. If I’m working with oil, grease, varnish, etc, I like to avoid having extra chemicals in my clothes. More superstition than science, but a preference nonetheless.