If someone doesn't have a car or the equipment they need to do their part in the band, that is an automatic no. Another one is when someone shows up with a 12 pack to each practice for themself for the night. Oh the things I have seen. It is always those that you have to help the most that screw things up the worst for the band. Cut that person out early and save the frustrations.
I can be flexible on the car, not everyone is in the same situation... Our "Geddy" is car-less but he is a well-equipped and consummate professional who can sing, play bass and keys simultaneously (not to mention a pleasure to deal with), so yeah, we'll gladly go pick him up. Also, he helps with load-in/out and I never saw a singer do that.
The weight of the gear is pretty brutal though. I estimated it at about 700 pounds of instruments alone. There's 7-8 guitars, 2 keyboards, a minimum 9-piece drum kit with rack for cymbals and percussion, as well as bass pedals, amp racks and speaker cabs. It take a minivan and an SUV tp lug it all. Having people willing to help is a must.