it's normal to feel that way, last year on the HSC fb discussion page, the ppl who received early entry offers seemed very very nonchalant about the HSC, even people I know personally stopped giving a shit about HSC once they received early entry, which is understandable because why would you care/work so hard if you already got what you wanted. but that's the thing, not everyone knows what they want, some students are deadset on law or psych or engineering, and so when the early offer comes through there's no further reason to try in the HSC. but many ppl don't know what they want so even if they have some early offers up their sleeve, they might still want to get a high ATAR and consequently widen their options
either way, no one should feel ashamed abt their attitude towards HSC, it's definitely normal to not care once you have early offers but it's also normal to still care