That's just making it easy to get.
Making rain more common would lead into endless farms of Ice golems, I'm pretty sure people would get a way to do that.
Nimbuses are already annoying when I'm not even in need of the Rod, and I get something like 10 Nimbuses spawns in the ... whole rain period, It can varie a bit doe
And increasing the drop chance? That'd be so easy to get, meh