Why Plomb?
They are good steel, and the 'pebble' versions 'look pretty'.
Seriously, tho, the generality of hand tools made by the best makers, from the mid-1930's to the mid-1950's, were the 'high-water-mark' of quality. If you use tools to earn your pay-cheque, you literally can't afford anything but the best.
There are subtleties of 'feel' between different makes of best quality hand tools......one make may just 'feel better' to one user, another make may 'feel better' to another, its purely a 'personal preference'.
Some tool users prefer the feel of Plonb tools, just as some prefer Snap-On.
Actually, most all of the best quality makes were equally good at turning a fastener, but when you are trying to 'make time' on a job, often getting into a contortion to access this or that inconvenient fastener, the tool which 'feels best' is the one to use.
Personally, I've been using Plomb and P&C tools for a great many years, now, many of which were from my father's old machine business, back in the '50's.
They are as useful for their purpose now, as they were half a century ago, i.e., with reasonable care, they'll never break or wear out. In all fairness, some of my tools are Williams, Armstrong, and other 'best makes' of the period, and equally serviceable......as an example, I tend to prefer the 'feel' of a Williams ratchet to that of a Plomb.....but only just slightly so, a subtle difference in handle shape which makes the Williams easier to hang onto when slippery with oil. Rather obviously, the fastener doesn't know what make of wrench turns it.......but I need the confidence that the wrench won't break or slip, and risk an injury to my hand, so I've no 'oriental brand x' tools whatever.
Risking injury to one's hands over the price of a wrench is an ultimate 'false economy'.
Now, 'collectors' are a different story. Personally, I tend to think its rather 'silly', a waste of useful working capability, when some folks collect up dozens of this or that make of tools, and just put them on a wall for display......but they've every right to do that, if they choose, its their $$$ and their option.
cheers
Carla