Yea, we've all seen stories where "Stepping on a butterfly" can change everything drastically, but, it's just as possible stepping on it will have no effect.
We'd already met the Vulcans when Vulcan was blown up, so, the fact Vulcan has been blown up doesn't necessarily need to change anything we're seeing with regards to people who exist and where. Now, of course, any Vulcans may have a drastically changed present, some may never be born, etc. But, someone from Earth, such as Captain Picard, would have to have his parents meeting be affected by Vulcan still being around, such as a mission they went on together in relation to the Vulcans, where they met or a Vulcan who was killed in the destruction of Vulcan saved one of their lives in the Prime Time line, etc.
So, the further removed you are from your history revolving around something that was changed the less likely that change is going to affect you.
Certainly the desctruction of Vulcan may change your timeline, but, it's just as likely not to have.