Sorry in advance for for the rant...
I personally believe it's self diagnosis and a lack of understanding of what PTSD actually is. When measurements of basal, cerebral-spinal-fluid corticotropin-releasing-hormone, circulating catecholamine levels, and CB1 receptor concentration can be legitimized as biomarkers then we will be able to accurately diagnosis PTSD. Currently we use the DSM as a self-confirming ouija board for psychoanalysts to justify their validity by pretending to be scientific. That book is very destructive and makes normal people seek psychiatric and therapeutic treatments which they do not need. That's why most doctors who own one won't let laymen read it, unfortunately the internet made that possible.
I am a huge believer that PTSD has become synonymous with "anxiety from an identifiable stressor(s)". It seems any type of anxiety that has a perceived, inorganic cause is now considered PTSD to an uneducated person. I frequently see people who think that anxiety has an organic cause and PTSD is simply anxiety from a stressor rather than innate biology.
Some leading experts are even talking about labeling PTSD as a "stressor and trauma related disorder" to distinguish it from anxiety disorders. PTSD is from repeated responses to fear (stress response from a real threat) and cognitive distortions or implicit memories from PTSD lead to anxiety (stress response to a percieved threat). PTSD is more of an issue with conditioned fear responses leading to pathological, implicit memories and physiological and psychological disorders arising from those memories activating the amygdala which is activating the Hypothalamic-Pituitary-Adrenal Axis which is messing up hormones. Anxiety is similar, some would argue the same mechanisms are at play, but it doesn't involve implicit memories that "trigger" the response or even necessarily involve a stressor. It can simply be caused by a cognitive distortion.
This is important to distinguish correctly. Treatment is different. Talk therapy typically works much better for anxiety. Someone with PTSD may not even be aware of their reaction (if implicit memory triggers the anxiety) and therefore things like cognitive behavioral therapy don't work as well. There is also a much greater rewiring of the connections between things like the amygdala, hypothalamus, cortex, striatum, etc. Hence all the focus on psilocybin and other neurogenerative agents that might help strengthen certain pathways. PTSD is also generally considered more permanent than most causes of anxiety are. Addiction, depression, and dissociation are also a greater concern in PTSD than anxiety disorders.
Reading about human behavioral biology can really help differentiate between these similar conditions. At first they seem nearly identical but after awhile you realize how extremely different they are. I strongly encourage Robert Sapolsky's lectures and books. They are easy enough to read, not like a normal biochem book.