Sometimes they're in the handicap stall.

Most places in England I've seen have an accessible toilet (for wheelchair users etc) in addition to male and female blocks, and the baby changing is in the accessible one.

The (admittedly half dead) mall near us has a "family restroom" for people with little kids that has one big room with sinks and changing areas and a separate adjoining small room with one regular toilet and one toddler size toilet. The big room even has a couple curtained off little alcoves with nice armchairs for breastfeeding moms if they want some privacy. It is SUPER convenient with a toddler and I wish they were more common.

Having been a dad of small children in the US, changing tables are very common in men’s rooms. If you aren’t a dad who needs one, they may be invisible to you. Once I started looking, I found them in almost all the places where women’s room also had them.