The thing that got me interested in biology and geology later in life was finding out / realising that there is a continuum between them and also with chemistry

The thing that got me interested in biology and geology later in life was finding out / realising that there is a continuum between them and also with chemistry and physics (both of which I loved at school). I don't fully understand why they are separated and taught as separate things, I wonder what the rationale is, apart from expediency.