It's every bit as likely that Yoshida doesn't want to implement it because the community will do a better job of it, for free?
And no, having a parse tool doesn't always lead to toxicity no matter what at all. That's simply stretching the truth far beyond reality. There are plenty of people that parse purely for their own ends across a wide variety of content and have no interest in saying a word about it outside of their own private circles and statics. Where's the toxicity in using it purely for self improvement and optimisation?
And again no, SE officially adding one has absolutely no bearing on what penalties would be thrown for harassment for a couple of different reasons. Remember that this game has an exceptionally hard stance on verbal harassment, if SE were to make it very clear that this isn't acceptable with the release of a parsing tool then the reality is that the status quo really wouldn't change. You don't need to use third party tools to get account strikes which will rapidly lead into an instant ban, simply copying and pasting lines of NPC dialogue or asking to be kicked from a duty is enough to achieve that. There's no reason for parser related abuse to be treated any differently unless SE explicitly chose to which is incredibly unlikely to happen. This isn't FFXI or WoW.