My parents always, always tipped when I was growing up. Hairdressers, taxi driver, bar staff, waiting staff, chambermaids in hotels. I thought it was the done thing in the 80s and 90s (we lived in a smallish Welsh town).
Then when I started working during university holidays etc, and I worked in places where my parents had often taken me as a kid, I realized that my parents' attitudes were the exception. I've worked in pubs behind the bar, pubs with nice restaurants, as kitchen staff, supermarket work, café work and also as a hotel chambermaid (cleaning rooms).
I was tipped once in three months as a daily hotel chambermaid (cleaned 15-20 rooms), and that was 50p (this was 1996) and it coincided with a guest having left the loo in a truly horrendous state. I felt cheapened by his 50p tip when he left, it really upset me.
When I was working behind the bar, I think I was bought a drink three times over months and months of shifts.
When I worked as a waitress in a pub, I'd guess at about one in ten people tipped, and then it was a maximum of 10% of the bill, often less.
I always tip, by the way, at least 10%. Though I do agree that there are many, many jobs where workers are on low wages and tipping isn't the norm. Although I understand that these roles eg caring aren't ones that traditionally attract tips, if I were to use these services, I would find a way of giving a tip, I'd hope (eg a generous Christmas/Easter/birthday gift).