They could also get an exception and attend the working sessions remotely. But there's a chance that could lead to fewer opportunities for advancement for them, because they weren't there. Which sucks. It's not an ideal situation.
BTW, lots of enterprise sales companies already do annual "sales kickoff" events where they fly all their salespeople globally to a single place. It's not unprecedented.
You're not far off the description of parents of young and early school-age children. Kids are in school/daycare for part of the day, then at home, needing dinner, care, etc.
Salespeople know, when they take their job, that they'll be expected to travel for work. Developers may not expect that to be a requirement of their job.