Very old fashioned if true. There are plenty of reasons to want part time work. Parents wanting time with kids but not wanting to lose touch with the workforce; students wanting experience, contacts and extra money; retirement age people wanting something to do or still feeling like they have plenty to contribute; seasonal workers; musicians and other artists working part time somewhere like a cafe or restaurant; those recovering from injury or with some form of disability; etc.
I personally know examples of all of those, which isn't surprising given that while 67.1% of NZ adults are in the labour force, only 48% of NZ adults work more than 30 hours a week (2013).
I am pretty sure it is true. Students of course have student work (not sure if that can be called part time), but there aren't that many students. And parents have 52 weeks of maternity leave to share between them, although in most cases the mother takes everything except the 2 weeks earmarked for the father---which is the main reason there still is a wage gap, since if you aren't there for the yearly raise conversation with management then you lose out on getting a raise that year and will lag behind other people. Similarly with pensions.
So people don't want to work during the maternity leave given that it is fully paid---also you can't be fired for being on maternity leave meaning that if you are fired while being on it management needs to provide a genuine reason for firing you.
Seasonal workers don't really exist unless you are thinking of those Poles/Romanians coming for two weeks a year to pick strawberries---those aren't working part time though, but full time (if not more).
Pretty sure that most retirement age people either work full time or is on pensions---if they feel like needing something to do there is always voluntary work which many retirees do.
Don't know about musicians and artists, though at least the ones I know have full time jobs and then only are musicians/artists on the side. And professionals obviously aren't working part time.
Disabled people and people recovering from injuries on the other hand are working part time---at least to some degree. I think, but might be wrong, that they are the ones mainly working part time.