There's a ton of situations where that's not realistic. If you travel a lot for your job, not doing work when you have downtime like a layover isn't feasible. Timezones are also a factor, and that may be the only time where all parties could be available. Or they just want to get the work done in the time before their flight so they don't have to when they get back.

Some people who face reasonable trade-offs in doing so have a choice. Others who face unreasonable trade-offs have less of a choice. It's usually quite difficult to tell when it's a stranger you're overhearing without making assumptions.