I saw Black Mirror: Bandersnatch (2018) and got a dead end by choosing the option where the protagonist destroys his computer when his "finished" code turns up buggy. But instead of continuing the story forward, the show kept repeating that scene and asked me to make a different choice where he just hits the desk, thus indicating a dead end.

The protagonist is already frustrated to the breaking point at this point, as his demo was a failure with his boss, so I felt the natural reaction would be that he would destroy his computer; but the show said otherwise.

Strictly from a screenplay point of view, why were there dead ends like this in the story? Why didn't they lead to one of the filmed endings? Keeping dead ends in this novel approach to storytelling seems very odd.

PS: The answer to another question indicates there are more dead ends too

The show is based on the "Choose Your Own Adventure" series of books, and in fact the author of said books has sued Netflix over this series.

The point is, in the "Choose Your Own Adventure" books, your character could die, thus making for a shorter story. In the TV show, it must run a specific length, thus the dead end forces you to choose an alternate course of action to progress the story along.

Keep in mind, they're on a budget. It's easier (and less expensive) to force you to make an alternate choice than to actually script and film every possible outcome.

Of course, the simple fact is that you don't really have a choice. ;o)

Another reason it may be done this way to motif the video game concept. In some games, you don't always just die, as much as you may have some "players" left and can return to previous checkpoint. (ie: the difference between loosing something vs loosing everything/the whole game)

Checkpoints are locations in a video game where a player character
respawns after death. Characters generally respawn at the last
checkpoint that they have reached.**A respawn is most often due to the
death of the in-game character, but it can also be caused by the
failure to meet an objective required to advance in the game.
Checkpoints might be temporary, as they stop working when the
character loses all of its lives. Most modern games, however, save the
game to memory at these points, known as auto-saving.

Checkpoints might be visible or invisible to the player. Visible
checkpoints might give a player a sense of security when activated,
but in turn sacrifice some immersion, as checkpoints are intrinsically
"gamey" and might even need an explanation of how they work. Invisible
checkpoints do not break immersion, but make players unsure of where
they will respawn. Usually, if a player does get a game over, then
there progress will be lost, and the player would lose all of their
checkpoints.

"...why were there dead ends like this in the story? Why didn't they lead to one of the filmed endings? Keeping dead ends in this novel approach to storytelling seems very odd."

But also to go with Johnny Bones' great answer, the notion of different kind of endings also does not only point out that we don't have full control and that there are still limitations, but it also gives us a contrast to consider what an ending really is, which the creators behind Bandersantch seem to want us to contemplate, as they themselves have...

Even Netflix says that while there are five “main” endings, there are
multiple variants on each that they are daring viewers to uncover. And
Brooker and Jones are clear as to not “prescribe” one ending over the
others, especially because they couldn’t agree on what exactly defines
one.

“There were quite heated debates about what constitutes an 'ending,'”
says Brooker. “There’s a school of thought that says any time it stops
and you go back, that’s an ending. In Bandersnatch, there are endings
that are really abrupt that are still endings, in my mind.”

Besides, Jones points out: “In a world of parallel realities, maybe
there is no ending?”