On the one hand, if you don't believe in what your parents do, that's okay, as long as you still respect them for the work they did being your parents.

On the other hand, if you truly believe in something, and believe that it's critical to their well being and future, why would you NOT try and teach them about it?

Because not all parents take their children's words seriously. Many of them think they're right about everything because they're older and more experienced, which is true sometimes, but it still makes discussing serious subjects or convincing them they're wrong impossible. For instance, my dad heard SOMEWHERE that ~85% of the population is immune to covid and now keeps ranting about how absurd it is that we haven't opened all non-essential business yet, and I'm having a really hard time explaining to him that even IF it's true, risking 15% of the population is an awful idea. If it's hard to tell them something as simple as "don't go out during a pandemic", how do you expect me to contradict them on more controversial subjects? Last time I expressed a political opinion they just refuted it in a very smug tone. Imagine the right-wing version of those tweets that start with "um, sweaty" and end with "my sweet summer child" and you get a pretty good image of how it feels to try to teach them about my worldviews.