Joints are a pain on a straight spar, adding a crook in it makes it a monster. Straight spar, even if the platform around it curves. Unless you want two concurrent spars? A bent spar wants to twist with lift. That’s extra twist from normal flying twist. Swept/ tapered platform is twisting the spar too, with varying lift at each station. It adds up quick. There is a reason rectangle wings are used, so you don’t have to figure all the extra out.