Yeah I'm well aware how ASPD affects frames and kiting. It's just that sometimes extra MS lets me be ina better position to start DPSing.
I actually had 2 situations, and somehow I was Cait in ARAM in both cases. The games dragged so long everyone had at least 3000g surplus. They built extremely tanky and always dived straight at me. They were the likes of Olaf, Trundle and Singed. The extra MS helped me run back long enough for allies to soften them and force them to stop their chase and engage other targets.
In game 2, similar situation. They had 1 Vayne and 4 bruisers (Wukong, Voli, Trundle and someone), 6 items for everyone. If I get flipped by Volibear I'm dead. Having a Warwick in our team made picking Swifties over Berserker a no brainer for me specially given their slows.
ASPD definitely helps in kiting too, but the benefit of less attack frames doesnt kick in until you start attacking. Sometimes you just gotta run back and wait for them to blow majority of their CCs before you can start attacking. I had more than enough gold for a Zephyr/PD, but I wasnt happy at how low my MS was in comparison so I sold it back for Swifties again.
I think I need to reiterate thar I dont mean I will replace Berserker with Swifties. I just feel that in certain situations Swifties is a good alternative.