The allowances were payments from each living and they were expected to do the work of the Royals.
Take look at my reply #47. Just my two cents from my point of view as an American Citizen. I recognize that the British may feel differently about the Royal Family than I do and it is up to them, not us.
OK, but for whatever reason they didn't like the gig, and quit.
A lot of kids I grew up with had overbearing parents who insisted they become doctors, or lawyers, or expected them to join the family business. Some did, some didn't.
And most of those on either side went on to have great lives. One fellow from my high school's father ran a large radiology business - he was a doctor and had several x-ray clinics all over the city. His father was deeply disapointed when his sun graduated college and went to work in the software industry. But he became very rich at a young age as an early employee of Microsoft.
Everyone, even Royals, have the right to steer their own lives in their own direction. I know I would find being a professional "royal" stifling, so I have a lot of sympathy for them leaving all that behind.