So, after playing with a super toxic Caitlyn screaming at me to get boots after I had an 8 win streak with no boots. I'm here to explain why not. You really only need boots to get away? Even then 85% of your game is riding on people, like why waste it on boots when ur heal speeds you up? @Amenazzy you dumb coconut. I rather get another support item or item to boost the people I'm on rather than boots which give 10% CDR even when I'm at max from my support items. 
Lets put this to rest. Some builds lower the need for boots, others will require them. Additionally Your map awareness will be a significant impact on weather you should use boots or not.
Some a rule of thumb's. Do you get MS from your build Early. If no get boots. Do you run Inspiration? If yes, get boots Via magical footwear. Do you die a lot unattached, if yes get boots. If your winning games with your build with out them and maintain good vision control. Skip boots, you don't need them.
Boots can be handy. Especially Sorc's mid-late game. Ride the most fed guy on the team and your Qs and Rs do actual damage. Not worth wasting gold on just to get around though. Unless your team are idiots who run from you you're going to be riding them from base to lane, and if they are then you have bigger problems than taking an extra 10 seconds to get to lane.
You shouldn't be downvoted because your title is correct, she doesn't NEED boots but they arnt useless on her, sometimes you have a bad team that literally runs it down so you need to hop off of them and run away rather than procing your passive.
That and going sorcerer shoes just for the magic pen is pretty selfish since that doesn't help with her healing/shielding. Even if 
costs more, yuumi doesn't have a hard time applying grevious wounds to the entire enemy team with 
