Hi, you don't have to and nobody forces you to do it, but some folks want to know and want to choose a healthier option. That's the whole point of discussing such matters, to give people an idea of all the spects involved with the decision they make.
I personally want to know about what I'm doing (This is one of the reasons why I quit smoking once I weighted out pros andcons) Doesn't necessarily mean that such knowledge is going to change my decision regarding my vaping style but it could affect it. Let's say that in a year or two a series of studies comes out that will prove that higher wattage, more vapor and lower nic is in fact 4 times more harmful than mtl, then I would rather know that and I might reconsider my long-term choices.
Most folks would like to know this stuff. I'm not aware of any useful studies in progress. Flavoring chemicals are a vast unknown as far as inhalation goes. We use thousands of them. I saw the list for strawberry once, there were dozens in just that flavor. None of them have been tested for inhalation, individually or in the infinite number of combinations. It's hard to see how they could ever be tested. Not really practical to have large numbers of people in labs inhaling each one of those base chemicals for long periods of time. You could feed them to lung cells in a dish but that only gives you a hint of what happens out in the world.
Some people avoid flavors for that reason.
We are really just waiting for long terms studies of the health outcomes of vapers. Even then extracting results for different styles of vaping and different flavoring choices and different levels of nic would be hard. How many people vape the same stuff in the same way for long periods of time. What happens if one of the ingredients of Mango flavor is bad? People might use Mango for a while then move on. There won't be a control group of people who use Mango and nothing else for long periods.
My guess is that for the foreseeable future all we will have is some numbers for the overall effect of vaping on health. They could look at the mostly older group of vaping ex-smokers and compare them to a similar group of non-vaping ex-smokers.
I think I saw some results for inhalation of VG and PG. At least regarding their inhalation in work situations. Didn't seem like they were too worrisome.