Why did I let the Buddleia grow so high?

It was great to see this Comma butterfly  - in fact there were two of them on the buddleia this afternoon. The only problem was getting a shot at them - the Buddleia has grown over 8 foot high despite a serious hacking earlier in the year and now it would be a shame to trim it full of flower, but of course the butterflies like the top branches and even with a chair I was struggling to see anything other than underneath them! 
It's the first time I've seen Comma in the garden.
An extra treat tonight as the bats were back. I could watch them for hours doing circuits!