This is a very good point. Who looked after the children, as a matter of interest?
I do think that white collar and professional jobs were treated differently, probably because women doing those jobs were in direct competition with men, whereas the kind of jobs you describe were women's jobs and very low paid. My mother-in-law went into the Civil Service straight from school in the 1930s, doing routine clerical work, and didn't marry until she was in her 30s. In spite of her long service, she had to leave the job as soon as she married, because that was the rule. She was able to get another job in an office in the City of London, which she gave up when pregnant. Much, much later the Civil Service did a special recruitment drive trying to get some of these women back, and she returned part-time until she retired.
Meanwhile, my mother trained as a primary school teacher and was able to stay in the job after she married, but again had to give up when pregnant. There was no maternity pay back then and no maternity leave - those didn't come in until the 1970s. She might have been able to negotiate some unpaid leave from her job so she could have gone back soon after I was born, but a substantial chunk of her salary would then have had to be spent on a childminder, and those were in short supply and totally unregulated. Day nurseries were mostly unknown outside the big cities, and thin on the ground there. She started supply teaching a few years later, then part-time teaching, then full-time, then redundancy/early retirement in her mid 50s (mid 1980s).
A woman with a husband was expected to be supported by her husband. This was double-edged - not only did it mean some women were unable to build a career, but it made life very tough for the valiant few women who did battle on (who would have included widows, divorcees and women whose husbands were unable to work). Men got promotions and pay increases because they needed to support their families. Women were assumed to be working for pin money.
Not really surprising that the sex discrimination extended to a different pension age as well.