See, this is where I'm living right now. I'm getting ready to move and thus start a new band. I thought about just doing it as a three piece, but tracks would really help to fill out the sound (and, frankly, the advantages to using a click track and Ableton Live to automate lighting are too great to ignore, so we'd probably be playing to a pre-recorded "track" anyway, even if that track is just MIDI cues and transition audio cues to IEM).
If money was no object, it would be great to hire a second guitarist, a keys player, and a few backup vocalists, but taking 6-8 people on the road costs a lot of money. A gig that would put $3-400 in my pocket now turns into $100-200, especially if you have to add a second vehicle for gigs farther away.
Now that said, I've seen plenty of nightmare scenarios. Shared the bill with a band whose track didn't get unmuted in the mains but was on in their IEM. So they're dancing around while the drummer is randomly tapping cymbals - it's a keyboard intro to the first song (lead singer is a keyboard player, but she pre-records so she's free to roam around as the lead singer). They don't have any idea that anything is wrong until the track stops abruptly and they have no choice but to restart.
I watched a hard rock band whose entire show was played with a single thirty minute track. That was a tough one to sit through, particularly since every song started with a guitar line played on the track while the other guys stood around in the dark waiting for the song to get going. Found out later they had lost their guitar player and were still breaking in their new one... decided to use the new guy as a rhythm guitarist for the tour.
And then of course there was the young local band that was charting low on the Billboard hard rock charts. They ran everything direct - no live amps on stage. They also had tracks for backing vocals, anything synth-y, second guitar, and even some crowd response sound, which was particularly cringe-worthy.
If I go the track route, you can bet that I will not just be using the tracks from a recorded EP and muting the guitar, bass, and drums. I'll be starting over from scratch - a live show is such a different dynamic than a much more intimate recording.