Question: Why the need for this other coin? I'm no programmer but, couldn't they alter bitcoin itself to be able to keep up with the newer demands?
It's because bitcoin updates requires agreement by virtually 100% of the community and bigger blocks is something people have been arguing about for something like 2 years. A faction in the bitcoin community thus decided to break off from the main bitcoin chain and start their own version instead.
Segwit is a competiting solution to processing more transactions and one which bitcoin cash people do not agree with.