That's domestication
... in my book, anyway. Ruminants of all kinds, and dogs were also included (in some "pre-Columbian" NA cultures, when it was also a beast of burden, before horses).
It's a different thing entirely to expend resources with no ROI other than (usually) unconditional love... and there we're talking dogs and cats. (I just can't see the attraction in the smaller mammals, birds, or reptiles -- where's the brain to go beyond eat/sleep?)
So I say: 100% emotional. All else is post facto justification (such as, the psychological benefits, cf. pet visits to nursing homes, etc.).
For the record: I am a 'cat person' of long standing -- except in the past two years (and currently), I've had to do without.