Well, if we look carefully, we see that depends on the age of the padawan.
I dunno if this really counts, as Obi Wan is Luke's master for a day or two before he gets cut down. Same with Yoda - he gets a short training montage, and then Yoda fades away.
Gandalf is not in a master-apprentice relationship with anyone. He's not even a mentor. He's just an older advisor, and probably shouldn't be modeled as a PC in any event.
Obi Wan is not all that young there - he's on the verge of becoming a Knight himself, as the Council promotes him right after that fight with Maul.
This, as compared to when we first see Ashoka Tano in The Clone Wars, or Ezra Bridger in Rebels, who are much younger than Obi Wan as we saw him. At the start of their series, they are much less potent than Anakin and Kanan, respectively. It is only over time they grow to be able to fight side-by-side with their masters and expect to survive.