This is the main reason I cancelled Prime. They started advertising “More than just free shipping”, and I realized that I only used it for free shipping, and as Prime got more and more expensive I wasn’t getting any value from it.
Now I just put stuff in my cart until I have $35 worth of stuff, and get free shipping anyway. It’s not that much slower. An extra day or two usually, and it doesn’t bother me one bit. I can wait a little while for my $10 guitar strap and it’s not the end of the world.
I notice the same thing. I think it’s because they are busy moving it from a distant warehouse to one closer to you, because you can’t possibly keep all of the same crap in all of the warehouses. So it’s being transported, but not “shipped”, allowing them to take longer.