I was taught that "much" was used for the uncountable nouns and "many" was used for the countable ones. So, why do people often use phrases such as "too much money" or "so much money"?
Are these phrases grammatically correct?
I was taught that "much" was used for the uncountable nouns and "many" was used for the countable ones. So, why do people often use phrases such as "too much money" or "so much money"?
Are these phrases grammatically correct?
Yes, those phrases are correct. As to why, you have basically answered your own question: money is normally an uncountable noun.
Cambridge Learner's Dictionary includes annotations [C] and [U] signifying whether a noun is countable or uncountable in a particular meaning. For example, the entry for money (here) has the annotation [U], while the entry for table (here) has annotation [C]. And chicken has [C] for one meaning ('a bird kept on a farm for its meat and eggs'), but [U] for another ('the meat of a chicken') (here).