Is this wrong? "हमको शराब नहीं चाहिए" ?
It's not wrong. Report it so the contributors are made aware.
Can't we drop the pronouns? I entered
शाराब नहीं चाहिए।
but it was marked as incorrect.
Formal/Written Hindi is not a pro-drop language so you can't drop pronouns.
That said, it can sometimes be done in informal spoken Hindi.
Sure, why don't we drop all nouns while we're at it?
He's not totally pronoun - but then, he's not completely antinoun either.
Why can we use हमें and not हम here? Why would हम शराब नहीं चाहिए। not be correct?
The sentence literally translates to something like 'To us, alcohol is not wanted'.
With चाहिए, we need to use noun+को for nouns and the corresponding form (हमें, मुझे, तुम्हें, आपको, उसे etc) for pronouns.