There might be ideological reasons for some Bitcoiners to join certain pools. For instance, my understanding is that @OCEAN recently took a stance on ordinals and created a template (one out of three so people have the option to mine without filters) that filters them out when mining. They are willing to forgo premiums in transaction fees to "optimize"
for monetary Bitcoin transactions. So that is one alternate case.... 

 choice of company and a national entity earning the fees