Depression itself? No- I'd say anyone can experience it. As a label/diagnosed thing though- debatable. Put it this way- I once went on a guided tour of a WWII submarine. The man that lead us had served during the war. One of the group asked him about mental health- SAD syndrome (Seasonal Affective Disorder- lack of daylight,) PTSD, depression etc. and he said- no- it simply wasn't recognised back then. Did the people that worked in those dark, cramped, smelly, dangerous, isolated conditions still suffer? They must have. They couldn't even contact their families as regularly as officers can now. There wouldn't have been any leniency back then though- by the sounds of it. You were just expected to get on with it.
I think the same can go in a watered down fashion with people in regular life. If you happen to come from a family that doesn't believe in such things- you won't get the same support to go and be diagnosed. You could still have stuff wrong of course but- it won't be recognised- you'll still be expected to get on with it. There will be plenty of high functioning people with mental illness out there.
To an extent, I come from this kind of background. My Dad has issues with the labels of mental illness and depression and he scoffs at the idea of therapy. As a result- it was actually a friends Mum who finally encouraged me to go and talk to someone because I was really struggling. I wouldn't say I have severe mental health issues but- for what it's worth, I was diagnosed with mild to moderate depression by my GP after that.
Not sure I'd call it a luxury to be able to be diagnosed with something! Maybe it's also debatable as to the best way of treating it. So- say someone suffers with social anxiety and general anxiety/depression- which makes it challenging for them to work. I'd say- yes- it would be a 'luxury' to come from a family wealthy enough to allow you not to work. Of course- it depends on the severity of that person's issues. Obviously- if they are vomiting and freezing up- that's one thing but- if they just feel extremely uncomfortable and come home and cry- I know loads of people like that- including me. So yes- to an extent- it can be a matter of luxury/wealth as to how a person with problems is expected to function.
Plus- it may not actually be the best course of action to give them the 'luxury' of not facing their fears. I haven't made the effort to confront my mild social anxiety and as a result- it has only intensified- to the point that it inhibits me from loads in life. Basically- I've let it become debilitating for me. I'm not going to argue that everyone has a choice in that of course. I suspect some mental illnesses are debilitating from the start. Some likely start small though and become debilitating because we are given or give ourselves the 'luxury' of not dealing with them and facing them.
So- a long winded way of saying- I think certain conditions exist- definitely. Their diagnosis to me seems rather woolly though- so that can be a problem. It's how they are treated that involves this idea of 'luxury' though. Some people are pressured to just get on with life where there probably should be more lenience. Others may well have all their needs and vulnerabilities pandered to- when it may have actually helped them to have been encouraged to live a more outgoing life.
It hinges on diagnosis surely and that doesn't seem to be an exact science to me. So- that in my opinion is where the problem lies. I expect most people could in fact go to their GP today and get diagnosed with depression- by saying the right things. You can't fake a broken arm though. It's not to say people with mental illness are faking it. It's hard to judge the severity though because it isn't exactly something that can be measured. Any diagnosis that relies on us describing symptoms has to be less accurate than say- taking an x-ray. When I had gallstones, they asked me to rate the pain on a scale of 1-10. But it was like- I don't have anything to compare this to! I can tell you it's the most excruciating pain I've ever had. I can't compare it to pain I haven't experienced though! As a result- I put the figure too low and they ignored it for ages.