Really? I'd suggest you don't want them to have a positive expected value on leaving at a moment's notice rather than wanting them restricted, but in any case... the solution is to structure your entanglements and dependence in such a way that this opportunity is available to them if they desire it, not to try to force contracts and obligations onto them in order to restrict them.
Can you rephrase? I'm thinking things like "If we have a kid, we shouldn't split up even if we're a little unhappy" and "If I've quit my job to be a homemaker, don't stop giving me money without warning". Are you saying to avoid getting in such situations in the first place? Or are you saying not to marry jerks who will leave you and the kids in the dust?
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.