Yes, I might be in the 4th group. I started with serious ballroom training when young after falling in love with slow waltz after a dance with my dance teacher. Was never really competitive type of guy or wanted to perform, but it was the only way to get more knowledge about ballroom, because quality in social ballroom dance schools was low. So eventually I quit with competing and moved to other genres - first salsa, then wcs and zouk (and some other dances danced in those communities). AT is planned somewhere in the future. It was interesting to me to discover a different approach to dance in every of these genres.
What is strange here is that - in my area again - there is relatively big number of people who are interesed in improving themselves in salsa but without competitive ambitions. A number of people in salsa community are dancing almost every day, combining classes and social dancing (although the amount of knowledge you can get from local instructors is relatively limited). To some extent in AT community as well. But it's not the case with ballroom for some reason. I changed several hobby ballroom classes/teachers after quitting with competitive ballroom in the meantime, but it is problematic - classes being cancelled due to low number of students, some teachers were not good, students didn't show much progress, some good teachers didn't have enough time for that as they were occupied with competitors, always being asked to start competing again etc ... and people from salsa and AT communities never appeared in those classes (with only e few exceptions that quit very soon) ...