When kids get older and don't know how to swim it could be very dangerous. For example, if you go on a fun family vacation to Hawaii and you don't know how to swim, how could you jump off a cliff or go scuba diving or jump off the boat. Drop the mic.
Yes, all kids should learn to swim, because it is a basic skill, like riding a bike. Eventually a child will be invited to a birthday party at a pool, and it will be a safety issue if they cannot swim. Where I live, all kids also learn how to downhill ski. It is good to know basic things that are relevant in life.
Kids, with the exception of those with a disability that doesn't allow them to swim, should always learn to swim. This is good for safety reasons as many children each year drown in pools. This would help to prevent many needless deaths. It is also good for their self-esteem because they see that they can do it.