I can understand why would Clovis do this but why would his heirs and their descendants keep up the practice generations after generations?

Once a king reunified the kingdom by battling his brothers he would divide it upon his death to his children who will then repeat the circle for generations. And in the end since the winning kings needed the support of the magnates to win the crown he give them concessions and little by little the king's power erode and he only become first among equals (if he is still independent and not a puppet).

In hindsight it feels so easy to understand it feels like the natural course of things, did nobody at the time saw it coming?