In "Amok Time" Spock begins the pon-farr and requests the Enterprise to divert from their course to Vulcan to drop him off for the "marriage ceremony".
Why couldn't he just take a shuttlecraft alone while the Enterprise continued to their destination? This kind of situation would occur a lot in TNG and DS9, where you'd see a lone crew member rejoining the ship by shuttle after some sojourn of their own.
Some possibilities I considered:
Did shuttles not have warp capability in that era? (or not go at a high enough speed to put Vulcan in range)
Did they consider it and assume Spock would be in no condition to fly the shuttle? (I thought they could be computer controlled?)
Out of universe had the writers just not established shuttles as regular forms of transport yet?