How we cite our quotes: Section.Part (if applicable).Paragraph
Quote #4
But in ancient times, when no man could make a figure without the talent of speaking, and when the audience were too delicate to bear such crude, undigested harangues as our extemporary orators offer […] the faculty of memory was then of the utmost consequence, and was accordingly much more valued than at present. (VI.I.19)
Public speaking is still important for some folks today (like motivational speakers and politicians), but in ancient times it was much more of a requirement. If you wanted to make a name for yourself, you had to have both a flair for speaking and a first-class memory. Make no mistake, these guys were catering to a tough audience and only the best would do.
Quote #5
Particular customs and manners alter the usefulness of qualities: they also alter their merit. Particular situations and accidents have, in some degree, the same influence. He will always be more esteemed, who possesses those talents and accomplishments, which suit his station and profession, than he whom fortune has misplaced in the part which she has assigned him. (VI.I.20)
Like other virtues, certain skills or talents can be valued in some cultures or situations more than others. But what are the criteria for seeing something as valuable? Here, Hume returns to the magic word: usefulness. If someone has a head for numbers, they'd probably be a good accountant but wouldn't necessarily be a brilliant painter or actor. Hume acts like a career adviser here, emphasizing that skills have to be a good match for the job someone's hoping to succeed in.
Quote #6
Broad shoulders, a lank belly, firm joints, taper legs; all these are beautiful in our species, because signs of force and vigour. Ideas of utility and its contrary, though they do not entirely determine what is handsome or deformed, are evidently the source of a considerable part of approbation or dislike. (VI.II.3)
Usefulness doesn't just shape our views on people's behavior and personality traits. It also influences what we see as ideal physical features. Sure, it's not the only factor involved in defining what we may see as attractive/unattractive, but it plays a role. Since signs of fitness, health, and energy factor into our ideas about utility, it's only natural that we find them appealing.