However nothing changes for your character so it is a practical pause.
Quicksaving, if life places demands on your time, and reloading is likely the best way to freeze the game-state.
In a multiplayer game having one character pausing the world for everyone makes no sense and is considered bad design.
Most multiplayer games consider all games to be multiplayer, even if you are just running a single client.
Things can change for your character. For example, patrolling NPCs can enter your pause-bubble. Also, player experience is an (arguably the most) important consideration in game design.
Another reason: you can have unchained party members at different areas in the game (perhaps sneaking to enact an ambush). To enter TB mode, won't you have to go to every single party member individually? Whereas a full-game pause is a single command that affects all characters.
Quicksaving and reloading is not an adequate substitute for a full game pause, for many reasons. What if you're in the middle of a cutscene and thus can't quicksave? Just load up your newest save, which might be 10+ minutes ago??? Also, reloading a save is way more effort than pausing and unpausing, especially if you have a relatively slow computer that takes a while to load up a save.
Disagree that full-pauses in multiplayer "makes no sense and is considered bad design." It highly depends on the game. A full-game pause in Stardew Valley, for example, is incredibly useful.
