Ultimately vamps take energy from external sources in order to maintain a semblance of metaphysical and physical health. (The same rules apply to vampiric spirits because incarnate vamps can go out of body too, practically no difference between them without the body.)

But the reasons why their energetic bodies/forms need this energy is more complicated. In my response I was refering specifically to these underlying reasons.

A closed crown, leaking energy system, metaphysical damage or behavioural quirks are only a few of many reasons why some people need to take energy from any external source (energy addiction doesnt count because it is just a want rather than a need and damages those partaking in it over a long period of time.)

As for the vampiric existence being extreemly complicated....well, each vamp has a varied reason for being the way they are, each energy system is different and each has different reasons for and ways of gaining the energy they need to function.

Some are specialised to take only specfic energies. Some need copious amounts of energy or not at different times. Some frequencies of energy are harmfull or helpfull or completely useless. There are different rates of pulling and metabolising energies. different ways of taking energies depending on the situation, environmental factors, where the energy is from and how skilled the vamp is. Every vamp goes through stages in their lives where their needs may change dramatically from one extreem to the other. The places vamps get their energy from are often in direct correlation to how they obtain their energy and how much energy they need at the time.

Nothing about energetic vampirism is simple or fixed.

I could go on and on and on. There is so much that so many people don't take into account when they see energy vampires because to them it often all looks the same from the outside.

All I am saying is that I think it's important to take into account that each and every energetic vamp is as different and complicated as any other person (perhaps moreso that lots of people in some cases,) and unfortunately generalisations usually simply don't encompass at least half of the vampiric population.

Thats all I'll say because I don't want to dominate your thread with my own opinions. I hope I've made my points clear enough for you to follow.