Some people have a different life, the jazz pianist I've been working with for years was also a surgeon, he was very often phoned when we were rehearsing to go to the surgical room for emergency surgeries. When it's a trio and the guy his the solist, you adapt and play the repertoire he already knows without having to practice. So it was ok to me. You can't tell a surgeon he's got a lack of commitment when he has to save lives at any time of the day.Not practising between rehearsals is an indication of lack of commitment. I have run into that and I just said "I've done my homework - call me for rehearsal when you're ready to rehearse, not practice." But then, I'm an old fart. I have waning patience. Time is running out.
The problem was when the drummer started finding excuses for not praticing but had a 9 to 5 job only without any stand-by nights or week-ends. Yeah in that case, NOT OK AT ALL.