A lot of this rings true from my days working in hotels. You could work for Marriott or Starwood and hop between brands, but still be a part of that company. If you jump ship some people would get awkward and not know if they should talk to you. It's the strangest thing I've seen. At the same time it made the 6mo - 18mo tenures in startups seem super small and non-comital. Maybe it's more of an issue with larger companies.