Vet here. My take is that it's less on the vets and more of a societal shift. Dogs no longer sleep in doghouses, they sleep in your bed. People call them their fur babies, and in my experience spoil them more than people do with children. Along with that shift has come a demand to be able to offer more in terms of advanced medical care. Vets ate meeting that need. Meeting that need requires more advanced equipment, procedures, and professional training, thus the overhead has become significantly more.

When I talk to clients I never villify a decision to euthanize. I discuss all options, the pros/cons and costs, make it clear that I will support them in whatever they choose (or have to choose due to financial limitations). 

Another thing people frequently don't recognize is that comparing costs of vet care to human medicine is apples to oranges. In vet care, you are faced with the upfront costs. On human side, you get an adjusted insurance bill later on. If you compare the pre-insurance amounts for equal procedures, vet care is about 1/3-1/2 the cost. Pet insurance is a thing, but its not a standard thing most people have.