I have the LD curv 500TS. I gigged very often and yes, sometimes it rains. Loading in and rolling the speakers outside without a cover when it rains is moronic. I did it once with a bin bag over the speaker and I looked real stupid. So I did myself a favour (and so should you), I spent €65 on this water resistant, tight fitting and robust protection for my beloved speaker. Side flaps are great for reaching the handles.
Now I wish for the price of the Curv500 system those bags/covers were included to be honest, but for an extra few quids, it was an essential buy to protect the investment, so I would recommended the cover bag 100%. Even just for a peace of mind perspective.