This is because difference people have different preferences. Some people want some weight sharing (and the amount varies from person to person), while some want no weight sharing. Some want a lot of resistance / pressure from the follower's right arm, while others want very little.
There's no single way that will work best for everyone, thus people tend to fall into two camps, those that try to adapt to whoever they are dancing with, and those who won't (and they only dance with selected people).
Neither strategy is wrong, BTW. It simply comes down to whether you want to dance most of the tandas, or only a few (and some people are quite happy to only dance a few tandas with their favorite partners). Maybe in the beginning, I think it's best try to try to be sensitive and adapt to different styles, but typically, people develop preferences for certain things / styles, and obviously will try to focus on those things.