I've played a fair share of D&D --ah, the appeal to geezerhood--, and the lionshare of the campaigns have been no play = no XP (or at least no full share). And for the most part I had a blast playing that way.
In the game I'm currently running, there is only the party XP total. Whenever a player sits down to play, with what ever character, that PCh as that much XP. New join, replacement PC, alternate PC created out of player whim, old PC swapped back into play, etc.
Can't see myself ever going back to individual XP awards/totals. Unless the group I'm running for asked me to. Repeatedly. With bribes. Or threats.
Why?
For one, this system is a better fit now that my gaming friends are in there 30's. If my friend with the newborn misses half the sessions, do I really want to --effectively-- exclude him from the campaign?
The way I see it, I offer my players every incentive to play.
Is that fair? Well, its not like I hand out real currency at the end of every session. You want to feel like you earned something? Go start a successful business. Or volunteer at a homeless shelter. Or go for your grandmaster's rating in chess. Let's get something straight: nobody ever earned anything pretending to be an elf. And more to the point, there's no objective way to measure it. So while someone might talk about the XP they earned, another will talk about the XP given out, and its impossible to distinguish between the two.
Which leads to my last reason. I can't be objective. I instituated this full XP policy in part because I realized that I play favorites. Can't help it. I'm suitably impressed by the playstyles that resemble my own (and I laugh at the jokes I think are clever. In that way, like everyone else, I'm a tyrant). So instead of falling into a pattern of rewarding players for play the game my way, I try to average it all out and reward the group as a whole.
Except that it isn't really a reward at all. Just a way of quantifying an escalating series of challenges.
</rant>