LEC casters vs. LCK casters: Endurance and Stamina?

It baffles me how LEC casters change every so often in a single game day. Like one game it’s Drakos and Vedi, then suddenly just one or two games later…we have Medic and Dagda. Then sometimes, a third pair. ALL IN ONE DAY!!!

Whereas in LCK, you have just two casters casting two series that, now, frequently go the distance (i.e. 6 games per day from 2 BO3s).

Is it an issue of endurance and stamina? Do we just have too many casters in LEC? Too few in the LCK? What’s going on?

Please share your thoughts!