I was born in the mid-1950s and remember seeing people using peglegs into the late 1960s and even early 1970s. I clearly remember multiple sightings of an old woman (70-plus) who used a hoof-like leather-clad black pegleg like similar to the one shown above -- and she was not in any way poor, so peglegs must have been regarded as standard way back then...
Some years ago I remember seeing a mid-1970s (you know, NSU Prinzes, SPD Willy Brandt election posters, flared trousers, platform shoes) Super-8mm colour home movie taken in West Germany showing five or six leg amputees using peglegs to come and go to and from a prosthetic centre. I remember seeing recently amputated people using metal crutch-like peglegs in Britain about that period. I think their use worldwide, even as prosthetic training aids, ended about then. I think the reason was that peglegs were considered very crude and unsightly in that period. Cosmesis (meaning concealing the fact of the user's amputation and pretending they were fully-limbed) was seen as overridingly important then.
Me too! I find their sparcity, outgageousness, and crudity very s*exy. They make an unambigous statement that the wearer is a leg amputee and that they make no attempts to hide or conceal this reality, but rather emphasise it by making it apparent to all onlookers. (I will admit, however, that I find crutch walking sexier. Still, a pegleg is a must for the "Compleat One-Legger"!)
Light weight, as stated above. A fully functional adult's AKA pegleg can weigh as little as 100 grammes and 200-250g is ample.
The crucial bioengineering benefit, however, is low polar inertia. Low polar intertia means that the distal (far) end of the prosthesis (its "Pole") is as light as possible. This gives the pegleg excellent controllability when powered by a short and/or weak stump.
Aesthetic sensibilities on prosthetics have changed. Cosmesis has been less and less important since the mid-1990s at least. Today many amputees make a point of using obviously false, "in-your-face," even outrageous, limbs. Who knows?, peglegs might have a future with a tiny fraction of leg amputees whose needs (physiological, but also why not sociosexual?!) they might fit better than conventional prostheses.