I completely disagree on some of these:
Your ATAR never expires and most people make their switch just after first year. Especially if you want to move unis, reapplying with your ATAR through UAC is very common. But I was moreso talking about if you change your career goals halfway through year 12.
As for your dismissal of the imposter syndrome point, I am not suggesting that one boast about their ATAR to others, that is antisocial behaviour and weird. It is however a reflection of you being able to put it some hard work and study, and certainly gives an example of accomplishment that you can look back on. A lot of my friends have struggled adjusting to uni because they don't feel like they belong in the course, that they only got in through early entry or bonus points and that they are not smart enough. Obviously do not build your self esteem on an ATAR, but theres nothing wrong in personally feeling happy about your achievements, and it definitely makes you feel more deserving of your university admission.
As for the parents thing, maybe this is cultural. My marks definitely gave my Dad more joy than they gave me and I like seeing him happy.