Short Answer... Because English is crazy. 🤣 So many rules and so many exceptions to the rules.

You are correct in saying that "pasta" is uncountable but "noodles" is countable. To see why try counting both things: I have one noodle. I have two noodles. I have eight noodles. I have a million noodles. These all make sense. Maybe you're holding each of these noodles in your hand. I have one pasta. I have two pasta. I have three pasta. I have a million pasta. This doesn't make sense because it is not clear what is meant by a unit of pasta. Is it a bowl of pasta? Is it a cup of pasta or a bag of pasta? It is unclear and therefore not countable. More generally, for something to be countable, it needs to be a well-defined unit of measurement. In other words, when we count countable things, it is easy to visualize. For uncountable things it is not easy to visualize because it is unclear what is going on.

Amusingly, English has imported most of its words for specific shapes of pasta from Italian, where they are plural countable nouns - but because English speakers don't generally recognise the Italian plural forms as plural, we treat them as uncountable nouns. If we were being pedantic, we could decide to talk about one spaghetto, one tagliatella, one raviolo, as opposed to several spaghetti, several tagliatelle, several ravioli, but we don't :-)

Noodles can be both countable and uncountable, because it can refer to two different things: A type of meal, and a string of pasta. 1) I had noodles for dinner, but my friend had pasta. Both are uncountable. 2) I paid $20 for soup, and it only had two noodles in it! - Noodles is countable.

Pasta is the material, so it's uncountable. Noodle is an item, so it's countable. It's like saying 'wax' is uncountable, but 'candles' are countable. Why?