My guess is that it is primarily a function of all the rain we've had this year. I've noticed several perennials behaving a little more lax in their stature this summer.

All the baloon flowers I have seen around the neighbourhood need staking eventually. I have one plant that I tried 'pinching' this year and it is still standing, but leaning. A couple of years ago I started growing a dwarf form, same plant and flowers but grows only 6 to 8 inches tall. No staking required!!

Mine seem to grow in clumps which fit nicely into the plant rings which you can get at the dollar store.

In fact, I just put the rings around them this afternoon. They're only about 8 inches high now, but I prefer doing it at this stage so that they grow more upright.

Yes, I usually stake mine unless they are surrounded by thick clumps of other flowers such as tall phlox or Japanese anemones to help support their stems.