Hell is an unfair place, it is only normal to cling onto those of greater power to become stronger yourself. Or you're just a coward. Either way, those who worship higher demons are plentiful for good reason. Boons and bursts of power may be granted if you manage to talk up a strong demon or fiend. Worshippers need conviction and confidence to become successful. But if they do succeed, become well feared or respected among those of lower power.
Through your experience of finding those to worship, you can easily tell the strong from the weak. When rolling a insight check to see how strong a creature is, you gain advantage. Also, when conversing with higher-level demons/fiends, their DC's are lowered when it comes to persuading them. You know many of the well-known demons and can easily identify them to your party. As a worshipper, if you are following a higher demon/fiend, you may find yourself going on your knees to pray for minor boons in combat. Finally, you can easily identify other worshippers, if you roll a successful Arcana/Insight check, you can take a guess at what demon/fiend they may be worshipping.