I get that it's inconvenient, but lore/narratively there are reasons those classes work differently.
Narratively how spells work for prepared casters (Wizard, Druid, Cleric, Paladin):
-Wizard: This is the mage that literally learned magic from books, so for them the prepared spells literally represent what they studied the night before (or outside of combat in bg3)
-Druid, Cleric, Paladin: All three of these classes generally prepare spells through some type of prayer or mediation, since their magic is from some higher power that grants them daily spells.
Narratively how spells work for spells-known casters (Bard, Sorcerer, Warlock, Ranger, Eldritch Knight, Arcane Trickster):
-Bard: This is the one class that I could see having prepared spells (specifically lore bards), however I think of bard spells like a list of songs/poems that they know and are ready to perform at all times. With that being said, I could definitely argue that a good performer can learn new songs, but probably not at the same rate that wizards read books.
-Sorcerer: These casters have a specific type of magic flowing through them, and there spell casting is more like learning to channel what they already have. Therefore they learn significantly few spells than wizards, but learn more about manipulating what they have (I.E. meta magic)
-Warlock: Since a warlock power are granted to them by their patron (which they may or may not have a good relationship with) and they seem to keep a loose grip on their power levels (I.E. 2 or 3 spell slots), it would seem odd to me for a patron to allow a warlock complete access to any spells they could possibly cast.
-Ranger, EK, AT: The 1/2 or 1/3 casters generally represent characters that have managed to pick up a few spells to augment what they were already doing, but probably wouldn't have the arcane or divine discipline needed to know an expansive amount of spells
Everything above is very strongly based on class fantasy/lore and role playing, so I know some people wouldn't care about that at all. For those people I also ask this... If a Sorcerer could switch out spells like a Wizard, why would you ever play a wizard? From strictly a gameplay stand point they would be almost the same except wizards won't have meta magic. So this was a part of class balancing as well.