*OP - You are right. Being a SAHM is not a job because jobs take only about 8 hours per day, with a lunch break, and you don't have to work at your job over the weekends.
Being a SAHM is more like slavery. 24/7, no breaks, no days off.*
I work around 12 hours a day. I don't get a lunch break. I do work at home most weekends.
I get up with my DS at 5am. I feed him, wash him, change him, play with him, then go to work. Then I come home, play with him, feed him, give him his bath, read to him and put him to bed. Then, when he is asleep I do some more work.
At weekends I still get up at 5am but spend all day with him. I work when he has his naps. Ditto a "day off" from work. If we go away on holiday I do exactly the same thing in a different place (but a bit less work - maybe just e-mails).
I'm not complaining
I just don't get this idea that WOHMs get "breaks" and "days off" but SAHMs dont. That (saying being a SAHM is "like slavery" to quote a poster upthread) is the sort whiney, martyish bullshit that gets people's backs up.
None of us get "days off" or "breaks" from being parents. If a WOHM gets a day off from work they generally spend it being a SAHM. A SAHM probably would find a day at the office and being able to pee in peace a refreshing change. Short term.
You can't say one "lot" has it harder than the other. People have different levels of job, put in different levels of effort to raising their children be they working or at home. Some people have 1 child, have 6, some have loads of support, some have none. Everyone's circumstances are different
But none of us get a "day off" from being a mother.
And being a mother isn't a job. It's a fucking privelege. However you chose to do it.