You get what you put in. If you expect a sangha to support you for life, you should be expected to do everything they require of you. But if you want to be free to do what you want and be supported for life, that's just living on dole - may be possible in Theravada cultures, but everywhere else, it's frowned upon and more or less unrealistic.
If monks and nuns are sincerely offering service to their Buddhist communities, or engaging in serious study or retreat, I see no reason why they should not be assisted with at least the minimum requisites of life. Indeed, the Buddha indicated this was something very desireable.
I don't understand how supporting people who teach, study and offer service in a dharma context could in any way be compared to people who go on the dole because they'd rather not work.
In terms of offering one's life to an organization- you are right, for guaranteed security it is logical the organization demands guaranteed loyalty in return. The unfortunate side of this is that, from what I have seen, is that the organization becomes more important than the dharma itself. And the individual monk or nun must often sacrifice their own spiritual development in favour of the organization. If there is no spiritual development, which leads to an increase in mental qualities that benefit others, why ordain at all? Why not serve the organization in a lay capacity, if one will be given no facility for spiritual growth? Greater autonomy means greater uncertainty, but one is free to leave if an environment becomes unfavourable for spiritual developlment or makes it impossible to truly benefit others. It is up to the individual to decide which road to take.
Unfortunately, doing "everything an organization requires of you" means that often Sangha members end up unhappy, burnt out and more stressed out than the laypeople they are supposed to inspire with their cultivation. Hence why several of the larger organizations had to hire psychologists for monks and nuns that were having breakdowns due to high levels of work-related stress.
A monks' or nuns' primary responsibility should be to the dharma. Doing "everything an organization requires of you" sounds a little bit like working for a corporation to me. Doing "everything an organization requires, within reason, as long as it does not compromise ones' study, practice or dharma service" would be a more suitable outlook. After all we are talking about monks and nuns, not corporate executives. Hearing the teachings, contemplating them,and meditating on them should be the foundation of one's monastic life.