Lat. sumere = to take up, to bear, to adopt. Con, an intensifying prefix = together, altogether. 'To ingest' is only one extension of that idea. Modern commercial consumerism, implying acquisition (principally) and exploitation (literally, not emotively) makes the root meaning very clear. I cannot concur with your understanding of the term.
And frankly, I am no-one's client until I choose to be, and before I petition them and am accepted as a client = dependant. I am a customer if I bestow my custom upon a supplier. I happily admit to being a user of software in that I feed it to my ravening flock of Macs.
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