I guess the codepoints of UCS and Unicode are the same, am I right?
In that case, why do we need two standards (UCS and Unicode)?
They are not two standards. The Universal Character Set (UCS) is not a standard but something defined in a standard, namely ISO 10646. This should not be confused with encodings, such as UCS-2.
It is difficult to guess whether you actually mean different encodings or different standards. But regarding the latter, Unicode and ISO 10646 were originally two distinct standardization efforts with different goals and strategies. They were however harmonized in the early 1990s to avoid all the mess resulting from two different standards. They have been coordinated so that the code points are indeed the same.
They were kept distinct, though, partly because Unicode is defined by an industry consortium that can work flexibly and has great interest in standardizing things beyond simple code point assignments. The Unicode Standard defines a large number of principles and processing rules, not just the characters. ISO 10646 is a formal standard that can be referenced in standards and other documents of the ISO and its members.