You are not the first to bring this up lately. I can confirm that it is refreshing.
The 6-star chest is a lot more rare, but I have seen it appear without spending crystals. It doesn’t seem nearly as rare when spending crystals though, and that’s something I have had to do quite a few times.
Someone who doesn’t realize there’s a 6-star chest or that the 5-star chest is almost as expensive. 
I feel your pain. I was sleepy and accidentally sold a 6-star weapon once. Fortunately, it wasn’t a weapon I can currently use (none of the picks were any good to me when I opened that particular 6-star chest).