The difference I see from people of my generation and people today is that nowadays people only seem to have one job. Dp and I were a bit extreme we held down multiple jobs for a year in order to try and raise the deposit for the tiny studio flat we bought.
This is another thing that does not translate well to modern life.
Even back when I started working (and I'm just about a millennial, al beit an older one
) Most jobs had fixed hours and days, and most people still had weekends and bank holidays off, so it was relatively easy to fit in a part time bar/waitress job (which I did!), because A: there WERE flexibile part time jobs in abundance, and B: your main job was usually pretty stable.
But now, a main full time job often requires evening and weekend work on rota, especially in jobs that used to be 9-5 so you had weekends and evenings free for PT work if you wanted. E.g. I have a friend who is a university lecturer, 15 years ago she'ld have always been out the door at 4/5pm. Now undergrad lectures can be at 7pm at night! AND she's expected to be available for marketing events/open evenings on a much more regular basis than in the past.
It used to just be doctors, nurses & police types who couldn't take second jobs, but now retail and admin and academics and all sorts are required to be available evenings and weekends and bank holidays in their primary job.
I had SUCH a cushty second job in my early 20s! I worked weekends and bank holidays in a posh restaurant, the tips were incredible, it doubled up as my social life because back then, hospitality staff had a free bar at the end of shifts. Nowadays hospitality staff are often on zero hours and weekends are covered that way. You won't get the job without being available and flexibly whenever they fancy calling you in, which you can't be if you have a main job.. besides which, your main job might call you in in weekends.. so..