Assuming you are referring to the companion limits, that was likely done for balance reasons since they are immortal in 'normal' mode. I happen to agree that from a common-sense standpoint the given reason is kind of silly, however it's probably the best they could do without having them be outright rude to the player about it (tbh I would actually like it if they did that, assuming it fit their temperament).
It gets worse at higher level since odds are good you have access to multiple suits of Power Armor, which would result in an unstoppable squad against almost anything even in hardcoe mode.
Then what's the point if you can't form a badass squad consisting of the deadliest people in the wasteland?
Having one companion out a time is one of the things that really bugged me. Three out at a time would have been great, have inter party banner, random discussions, each specialize at a certain task with party perks and player perks, infuse different tactics with different companions, etc.
However, greater groups of enemies would need to be added, maybe up the difficulty for each companion in the party, so on and so forth.
I don't want an unstoppable squad of allies, but a tightly knit squad of specializing companions, where tactics and approaches to battles are widely broadened.
I can only hope that they attempt a better party system for future Fallouts.