No, they’re not doing it because they’re bored and idle.
It’s just that not having a full-time job gives one a lot more flexibility as to how one will spend their time.
I was not aware that the relatively low level of haredi full-time employment was a matter of debate.
If you’ve got data that shows otherwise, please post it.
Here’s what “The Haredi Institute for Public Affairs” reports (bracketed words are mine):
As of 2017, the rate of employment among non-haredi Jews aged 25–64 was 87.8% among
men, and 82.1% among women, compared to 51.7% among haredi men and 73.4% among
haredi women of the same age group.
…[And among those who do work] Haredi men also work about 20% fewer hours on average than men in the general public.