Missing a session sucks. Falling behind because I missed a session sucks even more.
When I DM for a group, at Session Zero I lay out this crucial principle:
We all want to be there, so missing a session is punishment enough.
We all want to be there. It sucks to miss a game. I am not going to punish you by lagging your character behind everyone else’s because you miss sessions. The Dungeon Master’s Guide speaks to this a bit, in the context of experience points:
As an alternative, give absent characters the same XP that the other characters earned each session, keeping the group at the same level. Few players will intentionally miss out on the fun of gaming just because they know they’ll receive XP for it even if they don’t show up.
Usually, people are in it for the game, not the experience points.
Out of game problems require out of game solutions.
If it does become a habitual issue of missing sessions, I will never handle this out of game problem by punishing your character. We are going to have a conversation out of game, out of character, and see what we can do to make things better, or decide that group isn’t a good fit for you. But I will never punish your player character for it.
Discuss this with your players at a Session Zero.
I do not mean to say “my way is the best way”. Talk about this with your players. Maybe they’re okay with falling behind. Maybe they have the self awareness to know that possibly lagging behind in character advancement will motivate them to attend when they otherwise would not. This is okay too, as long as it is something you discuss with your table.