"people" and "money" previously were used to denote plural. Now we have "peoples" and "moneys". What is the reason for this?
The word "peoples" semantically differs from "people".
people [people peoples peopled peopling] noun, verb
- plural persons; men, women and children
- At least ten people were killed in the crash.
- There were a lot of people at the party.
- Many young people are out of work.
- plural persons in general or everyone
- He doesn't care what people think of him.
- She tends to annoy people. Use everyone or everybody instead of ‘all people’.
- countable all the persons who live in a particular place or belong to a particular country, race, etc
- the French people
- the native peoples of Siberia
As you can see above, "people" in the context of 3. means an ethnic group or a group of inhabitants occupying a specific region. The word may thus be in the form of "peoples" if you refer to multiple groups, the same way you could use "groups".
The two forms (peoples and people) are not interchangeable, meaning that it is incorrect to use "peoples" in the context of 1. or 2. or the other way around (with the exception of "a people", of course, which means a single ethnic group).
The same applies to "monies".
money [money moneys monies] noun
- uncountable what you earn by working or selling things, and use to buy things
- to borrow/save/spend/earn money
- How much money is there in my account?
- The money is much better in my new job.
- If the item is not satisfactory, you will get your money back.
- We'll need to raise more money (= collect or borrow it) next year.
- Can you lend me some money until tomorrow?
- Be careful with that — it cost a lot of money.
- uncountable coins or paper notes
- I counted the money carefully.
- Where can I change my money into dollars?
- uncountable a person's wealth including their property
- He lost all his money.
- The family made their money in the 18th century.
- moneys or monies plural (law or old use) sums of money
- a statement of all monies paid into your account
I have often seen "monies" used, but exclusively in legal text such as contracts, statutes and court documents. It is a term of art used in legal contexts only and is interchangeable with "funds".