In Armstrong's First Man, the Apollo astronauts were once again wondering what was the logic behind being in their spacesuit while performing the docking manoeuvre with the LM on their way to the Moon.

After all, the move is very gentle and why would there be a sudden depressurization, then?

Even if they wore one, how would astronauts be able to stand 5 more days (returning back) in their spacesuit, without ways to eat, drink , go to the toilet , etc...Because they'd be in the vacuum of space?

Even if they wore their spacesuit, the vacuum in their cabin would mean there was a breach somewhere and during re-entry, that would be fatal to the crew anyway.

A pressure suit would in no way have saved the Challenger or the Columbia crew.
I'm not sure the absence of a pressure suit for the Soyuz T 10A crew would have killed them, nor even the Soyuz T 18A crew.

The Soyuz 11 crew would have had been saved with a pressure suit, undoubtedly!
But when did the depressurization occure? Right after separation from the Orbital module, when the cosmonauts when tightly belted on their seats, unable to move much. Had the separation been done before re-entry, they would have been able to locate the leak and do something about it (especially if it's an opened valve, not a crack).
From SP-4209:
At approximately 723 seconds after retrofire, the 12 Soyuz pyro-cartridges fired simultaneously instead of sequentially to separate the two modules. The force of the discharge caused the internal mechanism of the pressure equalization valve to release a seal that was usually discarded pyrotechnically much later to adjust the cabin pressure automatically. When the valve opened at a height of 168 kilometers, the gradual but steady loss of pressure was fatal to the crew within about 30 seconds.
The thing is to located the valve away from the force of the discharge or to allow for the valve to be manually shut.

Anyway, it's a bit like wing and wheels for a spacecraft: only useful for a very short moment during a spaceflight and yet taking so much mass (or not being confortable).
The thing would be to build a spacecraft with valves away from danger...And pressure suits would not be necessary anymore.