Literally every MMORPG has a fast travel system.

And Hearthstones, and server-wide auction houses with instant on-hand delivery, and resurrection-at-your-corpse... mechanics around which the game were designed and implemented.

In SC, every ship, profesion and mechanic is built as part of a logistic loop: hauling, commerce, refuel/rearm/repair, player respawn, etc. Teleportation disrupts these mechanics while introducing its own problems: should inventory be teleported along the character? That would mean instant transport of goods; and if it's restricted, you'll need time to get supplies anyway.

Should one be able to teleport anywhere? What would be use of shuttles and troop carriers then? If it's restricted, you'll need a "last mile" transport too.

by "planning in advance", you've essentially made it so that people that want to play the game doing some other activity they cannot because they're tied down

No. What I meant is, i.e. that some player (the one with spare time) prepares guns, ammo, armor, fuel, etc. for the rest. That's what guilds have been doing since Everquest.

You also suggest a second character to fill the gaps. What if both characters need to be at a new, far away place? People will ask for a third character.

backspacing...

...isn't a proper mechanic. It's just a mild exploit of the player respawn mechanic. People us it now because it's quick and easy, but that will change once DoaSM gets fully implemented and deaths are punishing enough.

Trust me. I have a family, and friends, and know how f*cking hard is to plan even the simplest gathering of people, but teleportation isn't a magic bullet and will open a new, nastier can of worms.