Like a pp said, it's the simplest explanation.
A lot have explained it's to cover pet smells, others have no proper ventilation or means to leave windows open.
A few like the smell as a finishing touch after cleaning.
Someone mentioned covering smells from an elderly relative to government them some dignity.
It's not dirty houses that have them, it's a broad demographic for different reasons.
People like alcohol, chocolate, caffeine, smoking, flying to holidays, Almond milk, processed food, Apple products, cheaply produced clothes etc.
They are all things that we know are bad for us, others or the environment but it doesn't stop people doing it.
Are you saying you don't do anything at all that would make others wonder why you do it?
That the world's population should have the same outlook on fresheners as you do?
They like the smell is the bottom line.
Why they choose to use it depends on each person.
Some don't care about the prospect of getting ill.
Some don't realise how bad they are.
Some choose to ignore how bad they are.
Some choose to take their chances, same as a smoker/drinker does.
Some don't care about the environment.
Some don't believe it's doing that much damage to the environment.
Some get comfort from the scents.
Some don't think too much about it and just like the smell.
Again, I know academia isn't a measure of intelligence but I can't believe you don't understand that people make different choices based on all sorts of reasons.
You mentioned being a scientist, does that mean all scientists in your field don't use the products you mention?
I know a food scientist who eats all sorts once in a while. Her reasoning being to have a little of what you fancy in moderation.
Why are there doctors with unhealthy life choices? Because they choose to smoke/drink or whatever.
All down to choice and you wouldn't choose something you don't like.