nah, this is just not something designer would expect to fail like that. The LED has datasheet, the datasheet have leakage current, it has no data on increased leakage over years, you plan for what you have.

What would help is not randomly planning for some of the segments to fail (they are multiplexed with other things, you'd have to put more diodes), but to just get slightly better/less cheap LED display

Only "choice" made here was sorting by price when buying components for the cheap device.

Don't underestimate the appeal of saving one cent per unit. So long as the costs are externalised, anyway...

Eh, I don't agree.

LEDs are diodes (Light emitting diode). Certainly this was a cost saving measure, but it's not a bad assumption that the LED wouldn't allow reverse current flow.

what happens when that diode fails?

It’s not exactly designed to fail, they just don’t care. If they could add a one-cent part that made it fail sooner, they wouldn’t do that either.

Capitalist profit motive strikes again. The invisible hand expands tech and the visible hand keeps making tech worse.

People usually respond to this by saying that it would be absurd to suggest the company did this for its own benefit, when anyone who engineers knows these are often caused by revising design to minimize costs... and increase profits.