Tyvek pants are $4 or less from construction supply companies.

Yes, I know they aren't super durable, and yes, I know they won't breathe great in summer heat.

But for spring/fall weekend hiking when you don't think you'll be needing them a ton and aren't doing long distance, is there any reason why not?

I have good shell pants for when I need them (high intensity off trail, and winter when wet could very well equal dead), but they're kinda heavy for 3-season weekend hiking.

Is there a downside I'm missing? At $4/pair, and high recyclability, I don't mind lack of durability for this purpose.