Why does the word its always look like it's missing the apostrophe?

Because it is.

One of the many oddities of the English language I've found baffling over the years. I was taught as a young lad that an apostrophe followed by s meant it was the possessive. Ie Dad's, Mum's, etc

If I meant plural no apostrophe ie Dads, Mums etc

Then you get to it. Because people abbreviated it is to it's where now the apostrophe is being used for another use ie to indicate the loss of letters when concatenating two words together eg Didn't, Don't, Can't etc for some odd reason now it becomes its for possessive but not it's as that's short for it is.

Where's the logic in that? 😂

Because 'his' doesn't have one either, nor do 'yours', nor 'theirs'. Pronouns do not use apostrophes.

Because we expect the possessive form when it’s only used as a contraction for "it is".