We have to justify our high salaries buddy 😉
But on a serious note, design is very subjective and every Top Dick and Harry will have a say about things. Product designers are ideally solving for end users but also have to keep stakeholders happy (tech and product leadership). On top of that there is pressure to finish things fast even though scope is not defined. If we are able to convince leadership on designs, we have to convince engineering that the solution is feasible.
Wrt complex topics during office presentation, it’s important to cover topics others are not aware of. Else people will complain “yeh sab hume bhi aata hai (we already know this topic)”.
I can’t speak for every designer, but this is my pov based on past and present t experience.
Cheers.