I believe the idea of a therapy session is a technical one. When Freud had patients of independent means (that have tons of money) he had 5 sessions a week for a few years, when it's part of public health care insurance (poor folks), it's become 30 sessions tops, and the patient is announced that most work is done between sessions.
Brick and mortar clinics, are rooms with couches and people, that you have to come to, and meet face to face. I believe they act as bottlenecks in a lot of cases, as the question of matching the best specialist to the most needing patient, becomes a financial and geographic matter. Online therapy offers a lot of people access to therapy.
Reading the state of the art literature on online therapy makes me feel like there's a big lag in the definition of "online" compared to other services. I mean, when you say that you get your news online, do you mean that you get it on your computer screen instead of on paper? Or do you, perhaps, mean that you get it all the time? Or maybe even, that you are connected with tons of current content updates relevant to where you are, what you buy and what you do?
Same goes for online psychotherapy. It is not only that we can reduce the cost of couches and waiting rooms. Not even that a specialist can be accessible around the world. It's some app that tells you that since you started yoga, your anxiety levels lowered consistently, and that people who benefited from yoga like you, also found similar benefits in calling grandma. All this without a session.
*This is where someone shows me I've missed something great and fantastic in my research.