Commercial success has never been a reason for passion and development in any area. Often commercial success is a result of it and not the cause. If salsa goes mainstream, we will be tearing our hair and complaining a lot more. Going mainstream always has a cost associated with it.
What you enjoy is fine. The question is why the skills in the craft not improving. Personally to me they either seem stagnant or declining. Something that I don't seem to observe elsewhere.
But financial gain does play a role in whether someone wishes to improve their craft to the highest skill attainable.
You are right. I don't think commercial success is a reason for very passionate people to improve their craft, but it's a reason for a lot of people.
If someone is bad at salsa, they will just quit. Salsa has a very high drop out rate among beginners with good reason - it's friggin' hard!
When I was into photography, I went hard in the beginning because there was always something more to look forward to and more gear to buy. I probably spent more on photography in 3 months than I have dancing 10 years in salsa. There is a huge incentive to spend in photography, and because of that, there are tons of resources online for every thing photography related.
Can people go hard in salsa? Sure, but you reach your ceiling much faster - as in you know much sooner whether you will continue after a few weeks/months. It's also incredibly easy to get discouraged because of the social element (rejections and the like..). I often hear people say "well, I suck at salsa, but that's why I have a day job.. I feel sorry for people who do this for a living." Salsa is just not an activity that gives people incentive to improve as much as other hobbies.
All in all, I would say the reason you don't see people improving across the board is because of 3 main factors:
1) many people only look at salsa as a social activity where social status is more important than actual ability
2) lack of competitiveness as compared to other hobbies, sports
3) no financial gain to be had
It's not a big mystery why people don't talk about salsa or participate in discussions. It's boring for them.