I imagine the difference between English, which needs the as in "as much", and the asker's native language, which doesn't, is that "as" can be used in multiple ways in English:
- In comparisons - and it's the "as" in "as much" that tells me this is setting up a comparison:
I don't have as much money as you have.
- As an explanation, similar to "while", "because" or "so":
I don't have much money as you have not paid me for three months.
The latter is something people often say in colloquial speech, but it's sometimes frowned upon in formal writing and style guides.
As a native English speaker, "as much" primes me that this is a comparison. Without it, on hearing "I don't have much...", I think you're saying you don't have much in absolute terms, not compared to anything.
If I heard "I don't have much money as you have", I'd interpret the "as" as being an explanation for the fact you don't have much money - something like "I don't have much money as [a result of the fact that] you have...". I'd be wondering what I have that causes you to not have much money.
So for the sentence in the title, if I heard:
You're tall as your father
...nothing would make me think this is a comparison, and I'd expect the sentence to continue with an explanation of what it is about my father that causes me to be tall. For example:
You're tall as your father keeps sprinkling growth hormones onto your corn flakes each morning.