yes! i've had some of my friends who ask me why i keep stacks of weeds at my home, or sometimes outside. it's for this very reason! it's so useless to even sell em as you'll barely make money from it, but a lot of DIY's needed it.
Yeah I always keep at least one slot of 99 for the same reason! Even with Leif buying it for twice the price it's still not really interesting money wise, so I'd rather keep it for when I need it