system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If ballet dancers need to mutilate their pointe shoes before they can be danced in, why are they still manufactured the way they are?
gpt
To add to the comments that are already here, professional dancers go through pointe shoes *extremely* quickly (often in a matter of days or weeks depending on things like their role, the rehearsal schedule, and the performance season). Pointe shoes have to be easily manufactured on a wider scale so that they can be available for any dancer to pick up a new pair at a moment's notice (with caveats for things like vamp style (think "toe cleavage"), box length, etc.). It's much faster to make several copies of a "standard" style than for a ballet dancer or their company to order, say, 10 pairs of their custom-made shoe and risk running out before opening night - or risk a shipment being delayed and not having any shoes at all. 

(Some dancers definitely do that, though, depending on their status and sponsorship opportunities.)

Since pointe shoes are mostly paste, cardboard, and satin, it also allows for the shoe to evolve *around* the foot as the dancer's body changes. Imagine if you had a bunion, and your custom shoe no longer fit around it: you'd likely have to get your foot re-measured, with no guarantee that the bunion would stay the same size. Or what if one of your feet is arched a bit lower than the other, and needs a thinner shank (the hard part that supports the arch of the foot)? It would be easier to modify the shank of a standard pair of pointe shoes than to go through several iterations with a maker.

Some dancers prefer "soft" shoes, which is where you'll see the B-roll of dancers banging their shoes on concrete. ("Soft" makes it easer to feel the floor against your toes and makes the foot look more sleek, but often comes at the cost of foot support for sustained, slow movements.) Hot tip: you can microwave your shoe to achieve the same effect on a less localized level! Some dancers who have low arches often also want to break the shank so that the arch of the foot is more pronounced. (You can do this by applying water to the shank in a thin line and bending it. It's very contentious on which way to bend it, though.) Scraping the point / top of the shoe box with a razor or sandpaper is just a way to reduce slippage by adding friction (either by taking the satin off of the tip entirely or just by roughing it up). That depends on what kind of floor you're dancing on - for instance, wood is really slippery, but vinyl Marley floors offer a lot more traction.

tl;dr: pointe shoes are an extremely specialized tool that depend heavily on a person's body and situation, which are always in flux, and any custom-made item is going to be "frozen" at a point(e) in time that may not be compatible with a dancer's body or situation on any given day. Also, standardized shoes cost way less!

Source: semi-professional ballet dancer (18 years)